At school, we have many rules﹣don't be n ,don't eat in class, …
We shouldn't waste water.Instead,we should (节约) it.
The students are having a (化学) class in the lab.
After working for several hours,he was t and fell asleep soon.
Bill u gets home at 6:00,but today he didn't get home until 7:00.
As we know,the m goes round the earth.