At no point south of the Han River _______ more than a mile.
| A．the enemy didn’t advance | B．the enemy advanced |
| C．did the enemy advance | D．didn’t |
Can you explain ________ the sun goes down in the west?
| A．why is it that | B．why it is that | C．how it is that | D．how is it that |
A huge amount of oil was spilt on the East Sea, the causes of ______ are still under investigation.
| A．it | B．that | C．which | D．whom |
--- Has James finished his report on his Enquiry Learning yet?\
---- I’m not sure. He _____ on it last week.
| A．was working | B．has worked | C．worked | D．had worked |
If you are traveling_ the customs are really foreign to your own，please do as the Romans do.
you may have, you should gather your courage to face the challenge.
| A．However a serious problem | B．What a serious problem |
| C．However serious a problem | D．What serious a problem |