May I swim in the lake, mum–No, you____________. Look! Here is a notice “No Swimming!”

In the playground I saw a boy ___ I thought was your brother.

s the first time you _____Chengdu —–No. But the first time I _____here, the citywasn’t so beautiful.

30. — Whyyoube talking so loudly while others are studying– I am terribly sorry.

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