Most birds find it safe to sleep in the trees, but ________they have eggs or young chicks, they don’t use a nest.
| A．why | B．how | C．unless | D．where |
34．He told us everything was all right；he was wrong，_________．
| A．though | B．too | C．yet | D．for example |
33．The little boy ran away_________I could asked him something about his lessons．
| A．until | B．when | C．before | D．Since |
32．—You are so strong．
—Yes，I often________in the gym．
| A．help out | B．work out | C．make out | D．turn out |
31．—Bad luck! I have left my dictionary at the dormitory．
—__________．
| A．Here is it | B．Here are you | C．Here it is | D．Here you are |
30．The extra room________very useful when we had visitors．
| A．had been proved | B．was proved |
| C．had proved | D．Proved |