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【单选题】

Organic Food
Organic farming was among the fastest growing segments of U.S. agriculture during the 1990s. The value of retail. sales of organic food was estimated to be $16 billion in 2004. According to the Food Marketing Institute, more than half of Americans now buy organic food at least once a month. Why is organic food becoming so popular
What is Organic Food
In December 2000, the National Organic Standards Board of the U.S. Department of Agriculture (USDA) established a national standard for the term "organic". Organic food, defined by how it cannot be made rather than how it can be made, must be produced without the use of sewer-sludge fertilizers, most synthetic fertilizers and pesticides, genetic engineering (biotechnology), growth hormones, irradiation and antibiotics. A variety of agricultural products can be produced organically, including produce, grains, meat, dairy, eggs, and processed food products.
"Organic" does not mean "natural". There is no legal definition as to what constitutes a "natural" food. However, the food industry uses the term "natural" to indicate that a food has been minimally processed and is preservative-free. Natural foods can include organic foods, but not all natural foods are organic. Only foods labeled "organic" have been certified as meeting USDA organic standards.
Organic Farming
The phrase ’organic farming’ — first appeared in Lord Northbourne’s book Look to the Land, published in 1940. But the truth is, organic farming is the oldest form of agriculture. Before the end of World War Ⅱ, farming without the use of petroleum-based chemicals (synthetic fertilizers and pesticides) was the only option for farmers. Technologies developed during the war were found to be useful for agricultural production. For example, the chemical ammonium nitrate (硝酸铵), which was used as munitions (军需品), became useful as fertilizer, and organophosphates (有机磷酸盐) used for nerve gas were later used as insecticide.
These days, farmers are switching to organic agriculture once again, but now with an ecologically based, systematic approach that includes long-term planning, detailed record keeping and major investment in equipment and supplies. Although it is still only a small industry, the number of organic farmers is growing by about 12 percent per year and now stands at more than 12,000 nationwide.
Organic Farming in the U.S. Today
The USDA’s Economic Research Service reports that in 1997, the latest year for which data are available, farmers in 49 states used organic production methods and thirdVparty organic certification services on 1.35 million acres out of a total of 828 million acres of farmland. Approximately two-thirds of the certified U.S. organic farmland was used for crops, and one-third was used as pasture.
Large farms, mostly located in the Midwest and West, produced processed tomatoes, organic wine gs and other high-value crops on a commercial scale, whereas numerous small farms, concentrated in the Northeast, specialized in mixed vegetable production for direct marketing to consumers and restaurants.
While organic food can be found throughout the country, California was the leader in production of organic fruits and vegetables in 1997, followed closely by Arizona, Florida, Texas, and Washington in decreasing order of total yield. Farmers and ranchers in 23 states raised a small number of certified organic cows, hogs and sheep. New York, Wisconsin and Minnesota were the top producers of organic dairy cows.
Production: Organic vs. Conventional The passage is mainly about the differences between conventional and organic fanning.

A.
As you can imagine, organic agricultural practices are quite distinct from those of "conventional" fanning.
B.
Organic farmers:
C.
feed soil and build soil matter with natural fertilizer to grow their crops use insect predators, mating disruption, traps and barriers to protect crops from pests and disease make use of crop rotation, mechanical tillage and hand-weeding, as well as cover crops, mulches, flame weeding and other management methods to control weed growth.As a last resort, organic farmers may apply certain botanical or other non-synthetic pesticides. Conventional farmers:,
D.
apply chemical fertilizers to the soil to grow their crops spray with insecticides to protect crops from pests and disease use synthetic herbicides to control weed growth.
E.
How Do I Know if a Food is Organic
F.
Look for the word "organic" on vegetables or pieces of fruit, or on the sign above the organic produce display. The word "organic" may also appear on packages of meat, cartons of milk or eggs, cheese and other single-ingredient foods. Foods labeled "100 percent organic" must contain only organic ingredients. Products containing at least 70 percent organic content can be labeled "made with organic ingredients". Those foods labeled simply "organic" must have at least 95 percent organic ingredients, by weight or fluid volume, excluding water and salt. Anyone who knowingly sells or labels a product "organic" that is not produced and handled in accordance with these regulations can face a civil penalty of up to $10,000.
G.
Foods grown and processed according to the federal standards will in most cases bear the seal "USDA Organic". As its use is voluntary, companies may choose not to display the seal.
H.
Why Should I Care if a Food is Organic According to the USDA, organic food production allows farmers to lower input costs, decrease reliance on nonrenewable resources, capture high-value markets and premium prices, and boost farm income. Organic agriculture also has many important environmental, benefits:
I.
It promotes sustainability by establishing an ecological balance to pr soil fertility or pest problems. In the long run, organic farms tend to conserve energy and protect the environment by maintaining ecological harmony.
J.
It enhances biodiversity, or the presence of multiple plant and animal species. Having a highly diverse genetic pool becomes useful in the future when beneficial characteristics can be tapped.
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【单选题】Organic FoodOrganic farming was among the fastest growing segments of U.S. agriculture during the 1990s. The value of retail. sales of organic food was estimated to be $16 billion in 2004. According t...

A.
As you can imagine, organic agricultural practices are quite distinct from those of "conventional" fanning.
B.
Organic farmers:
C.
feed soil and build soil matter with natural fertilizer to grow their crops use insect predators, mating disruption, traps and barriers to protect crops from pests and disease make use of crop rotation, mechanical tillage and hand-weeding, as well as cover crops, mulches, flame weeding and other management methods to control weed growth.As a last resort, organic farmers may apply certain botanical or other non-synthetic pesticides. Conventional farmers:,
D.
apply chemical fertilizers to the soil to grow their crops spray with insecticides to protect crops from pests and disease use synthetic herbicides to control weed growth.
E.
How Do I Know if a Food is Organic
F.
Look for the word "organic" on vegetables or pieces of fruit, or on the sign above the organic produce display. The word "organic" may also appear on packages of meat, cartons of milk or eggs, cheese and other single-ingredient foods. Foods labeled "100 percent organic" must contain only organic ingredients. Products containing at least 70 percent organic content can be labeled "made with organic ingredients". Those foods labeled simply "organic" must have at least 95 percent organic ingredients, by weight or fluid volume, excluding water and salt. Anyone who knowingly sells or labels a product "organic" that is not produced and handled in accordance with these regulations can face a civil penalty of up to $10,000.
G.
Foods grown and processed according to the federal standards will in most cases bear the seal "USDA Organic". As its use is voluntary, companies may choose not to display the seal.
H.
Why Should I Care if a Food is Organic According to the USDA, organic food production allows farmers to lower input costs, decrease reliance on nonrenewable resources, capture high-value markets and premium prices, and boost farm income. Organic agriculture also has many important environmental, benefits:
I.
It promotes sustainability by establishing an ecological balance to prevent soil fertility or pest problems. In the long run, organic farms tend to conserve energy and protect the environment by maintaining ecological harmony.
J.
It enhances biodiversity, or the presence of multiple plant and animal species. Having a highly diverse genetic pool becomes useful in the future when beneficial characteristics can be tapped.
.
Because organic agriculture utilizes practices such as crop rotations, inter-cropping, symbiotic associations, cover crops and minimum tillage, the length of time that the soil is exposed to erosive forces is decreased, which minimizes nutrient losses and boosts soil productivity. By not using synthetic fertilizers and pesticides, organic agriculture-reduces pollution of groundwater.
K.
Organic agriculture helps to minimize the greenhouse effect and global warming through its ability to keep carbon in the soil.
L.
Why is Organic Food So Expensive
M.
Prices tend to be higher for organic titan conventional products. As stated on the Web site of the Food and Agriculture Organization (FAO) of the United Nations (UN), certified organic products are generally, more expensive than their conventional counterparts because:
N.
The organic food supply is limited as compared to demand. Production costs for organic foods are typically higher because of greater labor input and because farmers don’t produce enough of a single product to lower the overall cost.
.
Post-harvest handling of relatively small quantities of organic foods results in higher costs because organic and conventional 0roduce must be separated for processing and transportation.
.
Marketing and the distribution chain for organic products are relatively inefficient, and costs are higher because of relatively small volumes.
.
The FAO also notes that as the demand for organic food and products increases, technological innovations and economies of scale should reduce costs of production, processing, distribution and marketing for organic produce.
.
Is Organic Food Better than Conventional Food
.
Organic and conventional food must meet the same quality and safety standards. Organic food differs from conventionally produced food simply in the way it is grown, handled, and processed. There is no scientific evidence to suggest that it is more nutritious or safer than conventional food. A recently published report indicates that organic food is less likely to contain pesticide residues than conventional food. Yet, according to the National Research Council, the traces of pesticides left on conventionally grown products are unlikely to cause an increased cancer risk. Also, if fruits and vegetables are properly washed, most of the chemicals can be removed. As for taste, that’s up to you to decide what you like best. In general, people tend to find that the fresher a food is, the better it tastes, regardless of how it was produced.

【单选题】磷酸盐包埋材料属于

A.
低熔合金铸造包埋材料
B.
中熔合金铸造包埋材料
C.
高熔合金铸造包埋材料
D.
铸钛包埋材料 E.以上均不是

【单选题】硝酸铵具有()

A.
助燃性
B.
腐蚀性
C.
毒害性
D.
以上答案都不正确

【单选题】硝酸铵具有()

A.
助燃性
B.
腐蚀性
C.
毒害性
D.
以上答案都不正确