Life is like riding a bicycle. ________ your balance, you must keep moving.
| A．Keeping | B．To keep |
| C．Keep | D．Having kept |
We have launched another man-made satellite，__________ is announced in today's newspaper.
| A．that | B．which |
| C．who | D．what |
There is no simple answer，__________ is often the case in science.
| A．as | B．that |
| C．when | D．where |
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 |
Whenever I met her，__________ was fairly often, she greeted me with a sweet smile.
| A．who | B．which |
| C．when | D．that |
By 16:30，__________ was almost closing time, nearly all the paintings had been sold.
| A．which | B．when |
| C．what | D．that |