刀、剪、缝针等70％的酒精浸泡消毒，需用（）
A.10分钟
B.20分钟
C.30分钟
D.40分钟
E.50分钟
参考答案：C
“I took part in the TOEFL. It was really hard.” “Did you ______ a lot?”
A．Have you studied
B．Did you study
C．Had you studied
D．Do you study
At minus 130°C, a living cell can be ________ for a thousand years.[ ]
A. spared
B. protected
C. preserved
D. developed
