2014年6月大学英语四级复习题及答案(第三套)_第3页

　　Tress should only be pruned when there is a good and clear reason for doing so and , the number of such reasons is small . Pruning involves the cutting away of overgrown and unwanted branches , and the inexperienced gardener can be encouraged by the thought that more damage results from doing it unnecessarily than from the tree to grow in its own way .

　　First , pruning may be done to make sure that trees have a desired shape or size . The object may be to get a tree of the right height , and at the same time to help the growth of small side branches , which will thicken its appearance or give it a special shape . Secondly , pruning may be done to make the tree heavier . You may cut out diseased or dead wood , or branches that are rubbing against each other and thus cause wounds . The health of a tree may be encouraged by removing branches that are blocking up the center and so preventing the free movement of air . One result of pruning is that an open wound is left on the tree and this provides an easy entry for disease , but it is a wound that will heal . Often there is a race between the healing and the disease as to whether the tree will live or die , so that there is a period when the tree is at risk . It should be the aim of every gardener to reduce that risk of death as far as possible . It is essential to make the area , which has been pruned smooth , and clean , for healing will be slowed down by roughness . You should allow the cut surface to dry for a few hours and then paint it with one of the substances available from garden shops especially for this purpose . Pruning is usually done in winter , for then you can see the shape of the tree clearly without interference from the leaves and also it is very unlikely that the cuts you make will bleed . If this does happen , it is , of course , impossible to paint them properly .

　　26. Pruning should be done to _____.

　　A)make the tree grow taller . B) does not protect them form the wind

　　B)get rid of the small branches D) make the small branches thicker .

　　27. Trees become unhealthy if the gardener_______

　　A)allows too many branches to grow in the middle

　　B)does not protect them from the wind

　　C)forces them grow too quickly

　　D)damages some of the small side branches.

　　28 . Why is a special substance painted on the tree ?

　　A)to make a wound smooth . B)to prevent disease entering a wound .

　　B)to cover a rough surface . D) to help a wound to dry .

　　29. A good gardener prunes tree ____

　　A) at intervals throughout the year B) as quickly as possible

　　C) occasionally when necessary D) regularly every winter

　　30 . What was the author’s purpose when writing this passage ?

　　A)to give practical instruction for pruning a tree

　　B)to give a gardener description of pruning

　　C)to explain how trees develop disease

　　D)to discuss different methods of pruning