Try not to cough more than you can _______ since it may cause problems to your lungs.
| A．check | B．allow | C．stop | D．help |
The young lady stopped and looked around as if_____ whether she was being followed.
A seeing B to have seen C having seen D to see
--- Remember, Dad, Thomas Edison got bad grades in school, too.
--- Stay in your room until you’ve _____ the electric lamp.
A invented B discovered C made D imagined
There isn’t much time_____ . shall we go now?
A leaving B to leave C being leftD left
____ he came back home that we knew what had happened .
| A．When it was | B．It was when | C．Was it when | D．When was it |
It was the training _____ he had as a young man _____ made him such a good engineer.
| A．what ; that | B．that ; what | C．that ; which | D．which : that |