________we will have an exam(测试) next week,_____ we have to go over our lessons.

He was riding to school         it began to rain.

____________ they are brothers, they look like each other.

---Who are they?
--- This is Jim ______ that is Dale. They are my good friends.
A or         B and         C but         D /

The city park will be cleaner ___________ people stop dropping litter here and there.

3D printers are still _____ expensive for most of us ______ afford.

He realized his mistakes and took action to reduce the loss _______ it was too late.

— They speak perfect English. How long have they learnt it?
— ______ they were seven years old.

________ Tom ________ Mary speaks good Chinese, so they can communicate with these Chinese students very well.

If all the plants on the earth die, _______ people _________animals will be able to live.