Carbon
dioxide from burning fuels is the most common of the so-called greenhouse gases.
| A．produced | B．producing | C．to be produced | D．having been produced |
---How long do you think it will be __________ China sends a manned spaceship to the moon?
--- Perhaps two or three years.
| A．when | B．until |
| C．that | D．before |
You’d better take something to read when you go to see the doctor __________ you have to wait.
| A．even if | B．as if |
| C．in case | D．in order that |
Tom is one of the boys who __________ on time.
| A．is | B．are |
| C．am | D．was |
__________ they will not come to join us, we have to change our plan.
| A．Seeing that | B．When |
| C．For | D．As soon as |
That is __________ the problem lies.
| A．how | B．when |
| C．where | D．what |