While listening to the concert, the audience is required to remain ______ and keep quiet.
| A．seated | B．to be seated | C．seating | D．to seat |
I think you should work harder ________ you are satisfied with the way things are.
| A．if | B．when |
| C．since | D．unless |
．Ram explained to his mother ________ he would get home late that night because of extra work.
| A．that | B．which |
| C．what | D．whether |
Air pollution is getting more and more serious, so we must take action ________ it is too late.
| A．before | B．after |
| C．until | D．when |
Sarah Brightman, ________ will fly to space in 2015, is the first woman to fly there in the field of music.
| A．who | B．that |
| C．which | D．whose |
The businessman wears a suit and a tie with a beard ________ the season.
| A．whatever | B．wherever |
| C．whenever | D．however |