The river will be dirtier and dirtier________we do nothing to protect them．
| A．since |
| B．if |
| C．unless |
| D．until |
Eddie was sleeping ______ Millie was watching TV.
| A．while | B．as | C．when | D．after |
His father and mother often argued ______ what TV programmes ________.
| A．with, to watch | B．about, to watch | C．about, watching | D．with, watching |
Of all the stars, the sun is .
| A．the big | B．the bigger | C．the biggest | D．big |
---____ will he be back?
---In a week.
| A．How long | B．How soon | C．How often | D．How many |
---Did you hear the rain?
---______ .
| A．Until 30 minutes |
| B．Until 30 minutes later |
| C．Not until 30 minutes |
| D．Not until 30 minutes later |