H1N1 control and prevention is a   to China as well as the whole world． 

Shelly had prepared carefully for her English examination so that she could be sure of passing it on her first ________. 

--Why do you choose to work in an international travel agency?---Well, you know, English is my ________. So it is my best choice.

The foreign teacher Mr. Halt has a strange way of writing. Here’s a notice from him, but no clear ______ of what he has written can be made at all.

That she hadn’t kept her ____ on her work resulted in the failure.