22．With ______ growth of the Internet, computer security has become ______ major concern for businesses and governments．
| A．the; a | B．the; the | C．不填; the | D．the; 不填 |
He wrote a letter ________ he explained what had happened in the accident.
| A．what | B．which |
| C．where | D．how |
The days are gone______physical strength was all you needed to make a living.
| A．when | B．that |
| C．where | D．which |
Happiness and success often come to those ________ are good at recognizing their own strengths.
| A．whom | B．who |
| C．what | D．which |
He may win the competition, ________ he is likely to get into the national team.
| A．in which case | B．in that case |
| C．in what case | D．in whose case |
There is no simple answer，________ is often the case in science.
| A．as | B．that |
| C．when | D．where |