医疗器械的基本质量特性是
A．有效性和适用性
B．经济性和适用性
C．安全性和可靠性
D．可靠性和追溯性
E．安全性和有效性
参考答案：E
It's not wise ______ think you are always right. [ ]
A. of you
B. for you
C. for you to
D. of you to
The famous actor keeps fit and athletic by __________ at the gym for an hour every morning.
A．making out
B．figuring out
C．working out
D．turning out
