Questions 47 to 56 are based on the following passage.
To call something "marginal" means it is not very good. Farmers have their own way to (47) marginal land: It is the last to be planted under good conditions, and has the (48) to be avoided under poor conditions. Low (49) soil is not the only reason land could be considered marginal. It might be in an area where rainfall is (50) or where a hillside might rise too steeply(陡峭地).
There are uses for marginal land, however. Most often it is used as grassland. Grasses provide excellent (51) for grazing (吃草) animals like cattle, sheep and goats. Grass seed can be bought from a foreign supplier or (52) grasses can be used. However, using marginal land for grazing is not a issue. There is a (53) of overgrazing. Cattle can damage the crops by eating down to the roots. Also, the weight of the animals crushes the soft and can make it too hard for growing. A(n) (54) way to reduce the harm is to move animals from one field to another. This method is known as rotational grazing (循环放牧) which is extremely important for marginal land.
Another use for marginal land is for tree crops. Studies have (55) that the white pine and loblolly pine (火炬松) are two kinds of trees that grow well on such land. They grow fast and provide good quality wood. Another tree is the poplar (白杨), found in many parts of the world.
Failure to take the care needed to protect marginal lands can make a bad situation worse. But good planning can 56 a marginal resource into a highly productive one.

• A) feed
• B) priority
• C) transplant
• D) effective
• E) limited
• F) define
• G) adequate
• H) transform
• I) discouraging
• J) quality K) native L) revealed
  M) prejudice N) hazard O) recovered

Questions 47 to 56 are based on the following passage.