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 usually done in winter, for then you can see the shape of the tree clearly without the interference from the leaves.

A:damage the tree B:heal itself C:cause the disease D:give the tree a desired shape

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 usually clone in winter, for then you can see the shape of the tree clearly without the interference from the leaves.
The wounds result from pruning will do the following EXCEPT______.

A:damage the tree B:heal itself C:cause the disease D:give the tree a desired shape

In the 1840s, the Mormons (摩门教信徒), who are a religious group, travelled west searching for a new home. Many Mormons lived in the state of Illinois, but they had been badly treated and finally were forced to leave.
As the Mormons travelled through the desert, they became discouraged. Then they saw a strange tree. The tree’s branches stretched out like arms. The Mormons thought the tree looked like Joshua, a hero from the Bible. The Mormons thought the arms of the tree were telling them to continue on their way; so they did.
They found a new home in what is now the state of Utah. In Utah they saw trees like the one in the desert. They called them "Joshua trees."
The Joshua tree was very useful. The Native Americans of the West used almost all its parts. They ate not only the fruit of the tree, but also its seeds and white blossoms. They used its leaves for shoes. From its roots they made baskets and got colours for their clothes.
Settlers in the West used the Joshua tree for firewood and fences. Unfortunately, they often needed to cut down the trees. Some of the trees were as tall as 50 feet (15.6 metres). These trees were 700 or 800 years old. The Joshua tree grows very slowly. It grows only about one inch (2.54 centimetres) a year.
By the beginning of the 1900s, most Joshua trees had been cut down. People were sad that this strange tree had almost disappeared. In 1936, the Joshua Tree National Park was established in California. It has many kinds of interesting desert plants, including, of course, many Joshua trees. None of these Joshua trees are 50 feet. But perhaps some day they will be.
Which of the following is true according to this passage ______.

A:Settlers in the west lived on the Joshua tree B:The Joshua tree was valuable to the native American of the west C:The native Americans of the west could eat a whole Joshua tree D:If there hadn’t been the Joshua tree, the native Americans would have died out

In the 1840s, the Mormons (摩门教信徒), who are a religious group, travelled west searching for a new home. Many Mormons lived in the state of Illinois, but they had been badly treated and finally were forced to leave.
As the Mormons travelled through the desert, they became discouraged. Then they saw a strange tree. The tree’s branches stretched out like arms. The Mormons thought the tree looked like Joshua, a hero from the Bible. The Mormons thought the arms of the tree were telling them to continue on their way; so they did.
They found a new home in what is now the state of Utah. In Utah they saw trees like the one in the desert. They called them "Joshua trees."
The Joshua tree was very useful. The Native Americans of the West used almost all its parts. They ate not only the fruit of the tree, but also its seeds and white blossoms. They used its leaves for shoes. From its roots they made baskets and got colours for their clothes.
Settlers in the West used the Joshua tree for firewood and fences. Unfortunately, they often needed to cut down the trees. Some of the trees were as tall as 50 feet (15.6 metres). These trees were 700 or 800 years old. The Joshua tree grows very slowly. It grows only about one inch (2.54 centimetres) a year.
By the beginning of the 1900s, most Joshua trees had been cut down. People were sad that this strange tree had almost disappeared. In 1936, the Joshua Tree National Park was established in California. It has many kinds of interesting desert plants, including, of course, many Joshua trees. None of these Joshua trees are 50 feet. But perhaps some day they will be.
Settlers in the west used the Joshua tree for firewood and fences because ______ .

A:they thought the tree was useless B:they thought the tree was going to die C:they had changed their belief D:they had no other ways to deal with their problems

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 usually clone in winter, for then you can see the shape of the tree clearly without the interference from the leaves.
The writer’s purpose when writing this passage is______.

A:to describe how pruning a tree is done B:to discuss different ways of pruning trees C:to give practical instructions for pruning a tree D:to explain how a tree wound gets diseased and heals

Passage Three

A:Settlers in the west lived on the Joshua tree B:The Joshua tree was valuable to the native American of the west C:The native Americans of the west could eat a whole Joshua tree D:If there hadn’t been the Joshua tree, the native Americans would have died out

Traversing a binary tree in preorder is equivalent to （）.

A:Traversing the forest corresponding to the binary tree in root-first order. B:Traversing the forest corresponding to the binary tree in root-last order. C:Traversing the forest corresponding to the binary tree in breadth-first order. D:None of the above.