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【单选题】

第二篇
Where Have All the Bees Gone
Scientists who study insects have a real mystery on their hands. All across the country, honey bees are leaving their hives(蜂巢) and never returning. Researchers call this phenomenon colony-collapse(群体瘫痪) disorder. It is reposed that 25 to 40 percent of the honeybees in the US have vanished from their hives since last fall. So far, no one can explain why.
Colony collapse is a serious concern because bees play an important role in the production of about one-third of the foods we eat. As they feed, honeybees spread pollen(花粉)from flower to flower. Without this process, a plant can’t produce seeds or fruits.
Now, a group of scientists and beekeepers have teamed up to try to figure out what’s causing the alarming collapse of so many colonies. They hope to find out what’s contributing to the decline and to pr bee disappearance in the future.
It could be that disease is causing the disappearance of the bees. To explore that possibility, Jay Evans, a researcher at the United States Department of Agriculture (SDA) Bee Research Laboratory, examines bees taken from colonies that are collapsing. "We know what a healthy bee should look like on the inside and we can look for physical signs of disease. " he says. And bees from collapsing colonies don’t look very healthy. "Their stomachs are worn down compared to the stomachs of healthy bees. " Evans says. It may be that a parasite(寄生虫) the bees’ digestive organs. Their immune(免疫的)systems may not be working as they should. Moreover, they have high levels of bacteria inside their bodies.
Another cause of colony-collapse disorder may be certain chemicals that farmers apply to kill unwanted insects on crops, says Jerry Hayes, chief bee inspector for the Florida Department of Agriculture. Some studies, he says, suggest that a certain type of insecticide (杀虫剂)affects the honeybee’s newels system and memory. "It seems like honeybees are going out and getting confused about where to go and what to do. " he says.
If it turns out that a disease is contributing to colony collapse, bees’ genes could explain why some colonies have collapsed and others have not. In any group of bees there are many different kinds of genes. The more different genes a group have, the higher the group’s genetic diversity. So far scientists haven’t determined the role of genetic diversity in colony collapse, but it’s a promising theory, says Evans.
Where Have All the Bees GoneResearchers are seriously concerned with the phenomenon of colony-collapse disorder because ______

A.
honeybees help produce one-third of the foods we eat.
B.
parasites on bees may spread everywhere.
C.
honeybees cannot find enough food elsewhere.
D.
honeybees feed on flowers.
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【单选题】Many Americans harbor a grossly distorted and exaggerated view of most of the risks surrounding food.Fergus Clydesdale, head of the department of food science and nutrition at the University of Massac...

A.
They overlook the risks of the food they eat.
B.
They overestimate the hazards of their food.
C.
They are overoptimistic about the safety of their food.
D.
They overstate the government's interference with the food industry.

【单选题】线虫纲寄生虫的生活史()

A.
都属土源性蠕虫联
B.
都属生物源性蠕虫
C.
多数是生物源性蠕虫,少数是土源性蠕虫
D.
少数是生物源性蠕虫,多数是土源性蠕虫
E.
以上到对

【单选题】可引起畸胎或死胎的寄生虫首先应考虑

A.
杜氏利什曼原虫
B.
间日疟原虫
C.
刚地弓形虫
D.
恶性疟原虫
E.
溶组织内阿米巴

【单选题】细菌性烂鳃病与寄生虫性烂鳃病的相似症状是( )

A.
病鱼体色发黑,尤以头部为甚,鳃上黏液增多,魍丝肿胀,严重时鳃丝末端缺损,软骨外露
B.
发病晚期出现"开天窗"
C.
鳃盖充血、出血
D.
上下颌红肿