________ in his paper, he didn’t notice his teacher coming .
| A．Having absorbed | B．Absorbed |
| C．Absorbing | D．Being absorbed |
__________ the students who have taken part in the sports game is unknown.
| A．A great number of | B．A great deal of |
| C．A large number of | D．The number of |
_______, 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 |