(2009浙江宁波质检)Since David ________ downloaded a virus into his computer, he can not open the file now．

-Life itself tells us it is necessary to learn to be     .One can hardly survive without help from other people in the world.

High school students are supposed to be     about public services，which will benefit them in the long run．

It's quite strange that the man sleeps with his mouth ________ and his eyes________.

Unemployment in USA is        to remain high in 2010, and possibly for the next few years.