－The little boy can put on his shoes and ______ .
| A．take off them | B．take them off | C．take it off | D．take off it |
I really enjoyed your speech，________ there were some parts I didn't quite understand.
| A．because | B．for | C．until | D．though |
I enjoy fresh air so I always let the window open ________ it is really cold.
| A．unless | B．when | C．if | D．since |
We will have no water to drink ________ we don't protect the earth.
| A．until | B．before | C．though | D．if |
—You bought the car about ten years ago?
—Yes.________ it's old，it still runs well.
| A．Because | B．Since | C．Although | D．But |
Mark isn't coming to the concert ________________ he has got too much work to do.
| A．so | B．until | C．although | D．because |