We had to wait half an hour _______ we had already booked a table.
| A．since | B．although | C．until | D．before |
When it______ air pollution, Beijing faces the three “C” s-----cars，coal and construction，which lead to Beijing's thick air pollution.
| A．refers to | B．comes to | C．happens to | D．speaks to |
______ it have been the failure to pick up directions from the ground control that caused the air crash?
| A．Must | B．Could | C．Would | D．Should |
The one concern for parents and students is ______ if the student pursues their university education in a foreign country, the student will not have the opportunity to establish social contacts in China.
| A．what | B．that | C．whether | D．/ |
Not until the train pulled into the next station ______ her suitcase gone.
| A．Mary had found | B．had Mary found |
| C．did Mary find | D．Mary found |
In class, fewer of the students who are not ___ their studies sometimes ____the dying robots,not listening attentively.
| A．accustomed to ; are functioned as | B．accurate in; function |
| C．sceptical of; are functioned | D．addicted to; function as |