In the United States, there is always ____ flow of people to areas of ______ country where more jobs can be found.
| A．a; the | B．the ; a | C．the; the | D．a; a |
----You seem to have known Dr Smith for a long time.
---- That’s true. ______ he joined our club six years ago.
| A．Since | B．Until | C．When | D．Before |
----I don’t mind telling you what I know.
----You ________. I’m not asking you for it.
| A．mustn’t | B．needn’t | C．may not | D．shouldn’t |
The Mid-Autumn Day, which is a day for family reunion in China, _____ on September 12th this year.
| A．falls | B．fixes | C．lies | D．sets |
Three years ago in Beijing, my best friend, David, was hit by a car while riding a bike, _______ a terrible brain injury.
| A．caused | B．to cause | C．causing | D．being caused |
The rise in wood fuel use has _____ the disappearance of forest and the loss of habitats for pandas.
| A．belonged to | B．adapted to | C．devoted to | D．contributed to |