Compared with 2 million tons last year, our coal output has increased _____
three times; that is to say, our coal output has increased_____8 million tons
this year.
| A．to; to | B．to; by | C．by; by | D．by; to |
_______, the more exercise you do, the richer your knowledge will be.
| A．It is known to all | B．Which is known to all |
| C．As we all know | D．As is known to all that |
His mother happened _______ when his program was shown on Channel Young.
| A．watching TV | B．to watch TV |
| C．to be watching TV | D．being watching TV |
By the time he was ten, Edison _________ experiments in chemistry.
| A．had already done | B．already had done |
| C．was already doing | D．already did |
The businessperson wanted to sell his goods fast; ______, he chose his partner with great care.
| A．therefore | B．otherwise |
| C．for | D．however |
Do you know the man____ is talking with Tom?
| A．which | B．who | C．whom | D．whose |