问题
填空题
用所给单词的适当形式填空
1. Trees must __________(prevent) from being cut down.
2. They __________(plant) ten thousand trees by last spring.
3. The sheep __________(tie) to the tree has eaten a lot of grass.
4. I can easily hear combs __________(go) through hair.
5. Great changes __________(take) in our hometown in the last ten years.
答案
1. be prevented 2. had planted 3. tied 4. going 5. have taken