I think AI （人工智能） in many fields will to help us solve many problems in the future．（ ）
A．used, be usedB．is used, be used
C．used, useD．is used, use
Is this photo taken in Tibet？
Yes，you can see beautiful snow mountains in the _______of the photo．（ ）
A．expressionB．background
C．introductionD．shape
What were Helen and Sally doing when it began to rain heavily？
Helen was sleeping _______Sally was reading a magazine．（ ）
A．whileB．untilC．beforeD．after
Mum，_____ I go out to watch a movie？
Yes，you can．But you must finish your homework first．（ ）
A．mustB．needC．willD．may
We finished the rest of the dinner ______ silence after we heard what he told us．（ ）
A．onB．atC．inD．of
Eric is not going to Nanjing by ______ plane．Instead，he is taking ______ train．（ ）
A．/， aB．a， /C．a， theD．the， a