医疗器械的基本质量特性是
A. 安全性和有效性
B. 适用性和有效性
C. 适用性和可靠性
D. 维修性和经济性
E. 安全性和可靠性
The fresh air is sometimes humid from the()rainfall of this area.
A. numerous
B. abundant
C. plenty
D. substantive
The news()heard everywhere.
A. had
B. have been
C. was
D. are going to be
When pessimists()in their first attempt, they usually say, "I can't do this."
A. feel
B. fail
C. defeat
D. lost