1. His step mother did all she could help him.
2. I have nothing be afraid of.
3. She was made cry by her younger brother.
4. I came here buy the book you mentioned yesterday.
5. The teacher allowed Li Ming to do the experiment, but I wasn’t allowed.
6. The enemy had no choice but lay down their arms.
7. How do you dare climb the tall tree?
8. It took him ten minutes get to school.
9. We should serve our customers heart and soul.
10. I will come back to home tomorrow.
1. could后加to。could后承前省略了动词do,不定式to help him作目的状语。
9. 去掉to。serve 为及物动词，其后可直接接名词。
10. 去掉to。home 为副词，前不可用to。如：回家 go home
11. 去掉to。hear sb. sing (听全过程) 或hear sb. singing（听某人正在唱歌）