医疗器械的基本质量特性是
A.安全性和适应性B.安全性和有效性C.安全性和可靠性D.安全性和经济性E.适用性和有效性
参考答案:B
所谓蛋白质的初级结构是指蛋白质的()
A.一级结构
B.二级结构
C.三级结构
D.四级结构
—There are 60 students in my class and 44 of them use weibo veryoften.
—44? That means about_______of your classmates are weibo users, right?
A.half
B.one third
C.two thirds
D.three quarters