Passage 8 Trees should only be pruned w

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问题 Passage 8Trees should only be pruned when there is a good and clear reason for doing so and,fortunately,the number of such reasons is small.Pruning involves 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 leaving the trees to grow in their own ways.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 healthier.You may cut out diseased or dead wood,or branches that are rubbing against each other and thus causing wounds.The health of a tree may be encouraged by removing the branches that are blocking up the center and so preventing the free movement of airOne result of pruning is that an open wound is left on the tree and this provides an easy entry for diseases,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,or that there is a period when the tree is at risk.It should be the aim of every gardener to reduce the risk 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 produced especially for this purpose.Pruning is usually done in winter for then you can see the shape of the tree clearly without the interference(妨碍)from the leaves and it is,too,very unlikely that the cuts you make will bleed If this does happen,it is,of course,impossible to paint them properly.Trees become unhealthy if the gardener(  ).A.to help a wound to dryB.to covers a rough surfaceC.damages some of the small side branchesD.allows too many branches to grow in the middle

选项 A.to help a wound to dry
B.to covers a rough surface
C.damages some of the small side branches
D.allows too many branches to grow in the middle

答案 B

解析 在第三段中提到必须保证修剪后的伤口平滑、干净,因为粗糙的表面会减慢伤口的愈合速度。A帮助吹干伤口;B覆盖一层粗糙的表面;C损坏一些小树枝;D允许许多树枝往中间方向生长。结合四个选项,B选项:覆盖一层粗糙的表面,可知会减慢伤口的愈合速度,因此会使得树木变得不健康,故正确答案是选项B。
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