I enjoy _____ to learn their different tradition and cultures.

- Honey, this is a present for your birthday.- Ah! A pair of shoes, well-known-brand – Nike. I think it _______ comfortable:

---How do your parents usually go to work?---My mother usually goes to work _________  bus while my father ________ a bike to work. 

Tom was so tired that he fell _________on the bed and went to sleep

Pollution is a serious problem. Scientists have _______ some good ways to save it.