Healthy trees are important to us all.Trees16 shade,beauty,and homes for wildlife. Trees give us products like paper and wood.Trees can give us all this17 they are healthy.They must be well cared for to18 heath.
People spend much time and money to plant and take care of trees.Trees 19 the looks of homes,parks,businesses and public buildings. 20,people who love trees the most may be the ones who cause them injury.Of course,they do not do this21,They may not know about the kinds of things that harm trees.We should become 22 those people-caused tree injuries and avoid them.
Trees,like people,are 23 by changes around them.Construction of buildings is a 24 cause of tree injury. Trees are often injured by changes in ground level. Roots can be damaged when heavy building equipment25 them.Root injury,not trunk injury,during construction is most likely to kill trees.When homes are built,concrete,bricks, or too much soil is put around trees.This can change the 26 of water and air that the roots get.Trees with roots covered in this way cannot"27"They die within three to five years.
Putting a well around the trunk of a young tree may help.A young tree planted in a large well can 28 living in a well,When young trees are to be planted within large29 areas,such as parking lots,they should be planted in large wells.Trees should not be planted 30 all construction has been completed.You can prevent damage to older trees near construction sites by putting fences around them.
A、sum
B、amount
C、size
D、number
【正确答案】：B
