医院感染用的流行病学调查方法有()。
A.爆发调查
B.现场调查
C.病例对照研究
D.队列研究
E.干预研究
参考答案:A, B, C, D, E
——There'll be billions of people to watch the Spring Festival gala on TV tonight.
——I know. The whole world______.It's a really wonderful event.
A. watches
B. is watching
C. has watched
D. will be watching
钢材在外力作用下产生变形,如果外力消除后仍能恢复原状的特性称为()。