. ---Can those ___ at the back of the classroom hear me?
---No problom.
| A．seat | B．sit | C．seated | D．sat |
__________ he had not hurt his leg, John would have won the race.
| A．If | B．Since | C．Though | D．When |
I won’t call you, __________ something unexpected happens.
| A．unless | B．whether | C．because | D．while |
He was told that it would be at least three more months __________ he could recover and return to work.
| A．when | B．before | C．since | D．that |
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 |
You will be successful in the interview __________ you have confidence.
| A．before | B．once | C．until | D．though |