1. Remember to lock the door.

2. She ought to wash salads well in water.
3. He sings badly.
4. She worked late last night, and he did, too.
5. You ought to sleep soon.
6. How heavy is Tuan?
7. Because of her illness, Lan didn't go to school yesterday.

8. My mother prefers to walk rather than cycling.

1  to lock the door 

2  to wash salads well in water 

3 badly 

4 worked late last night too

5 not to stay up late 

7 lan was ill, she didn't go to school yesterday 

8walking to  cycling