The silence of the library is sometimes broken by a sudden cough or the sound of pages______.
A. turning B. turned C. being turned D. having turned
Wang Pin is an advanced worker in our company. He _______ for four years in Yangzhou University.
A. studied B. has studied C. had studied D. has been studying
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
