.
— I ‘ll ask our physics teacher to explain Newton’s Second Law of Motion, which she taught us yesterday.
— That’s just _______ most of the students haven’t understood.
| A．what | B．why | C．how | D．where |
The 13:30 train to Shanghai has been put off __________ the heavy storm.
| A．due to | B．in case of | C．aside from | D．except for |
You cannot take back your words _________ they are out of your mouth.
| A．before | B．whether | C．once | D．while |
—What’s that noise?
—There’s a truck stopping outside. It’s someone _____ something.
| A．deliver | B．to deliver | C．delivering | D．delivered |
Remember me to your parents when you _____ them.
| A．are calling | B．call | C．will call | D．have called |
_____ time, the teacher had us do half of the exercises in class and complete the other half for our homework.
| A．To save | B．Save | C．Saving | D．Having saved |