[单项选择]Trees should only be pruned (修剪) when there is a good reason for doing so. Many gardeners believe that more damage results from doing it unnecessarily than from leaving the tree to grow in its own way.
First, pruning may be done to make sure that trees have a desired shape. The object may be to get a tree of the right height, and 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. A tree may grow healthier by removing the branches that are locking up the centre 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 (进入) 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. Pruning is
A. the cut surface can heal more quickly
B. open wounds on the tree run the less risk of getting diseased
C. a gardener can do pruning more easily
D. the leaves can interfere

[单项选择]
Trees should only be pruned (修剪) 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 locking up the centre and so preventing the free movement of air.<
A. Because it can make trees grow taller.
B. Because it can improve the shape of the trees.
C. Because it can get rid of the small ranches.
D. Because it can make the small branches thicker.

[单项选择]Trees should only be pruned (修剪) when there is a good reason for doing so. Many gardeners believe that more damage results from doing it unnecessarily than from leaving the tree to grow in its own way.
First, pruning may be done to make sure that trees have a desired shape. The object may be to get a tree of the right height, and 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. A tree may grow healthier by removing the branches that are locking up the centre 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 (进入) 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. Pruning is
A. Pruning is necessary when there are unwanted branches.
B. Damage is done to a tree if it is left to grow in its own way.
C. Diseased or dead branches should be cut away if they are found to rub against each other.
D. Growing side branches often prevent air from moving freely.

[单项选择]

Trees 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 the cutting away of over grown 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 tree to grow in it sown way.
Firstly, pruning may be done to make sure that trees have 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 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 wou
A. several times throughout the year
B. as quickly as possible
C. occasionally when necessary
D. regularly every winter