We can overcome all the difficulties by_____ together．（ ）
A．workB．worksC．workingD．worked
— Hey, boy. You can’t cross the street now. You have to wait _______ the traffic lights turn green.
— Oh, sorry and thank you.
| A．when | B．until |
| C．while | D．after |
Mom was cooking ________ Dad was reading newspapers.
| A．as | B．when |
| C．while | D．since |
It’s late. David washes his face _______ goes to bed.
| A．and | B．but |
| C．so | D．or |
（）—Do you believe that paper is made ________ wood?
—Yes, I do. And you can see that books are made ________ paper.
| A．from; from | B．from; of |
| C．of; from | D．of; of |
Guangdong is ____ the south of China .
| A．in | B．on |
| C．to | D．with |