消化道溃疡出血的患者其粪隐血试验阳性的特点是（）A.出血量大且

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问题单项选择题

消化道溃疡出血的患者其粪隐血试验阳性的特点是（）

A.出血量大且呈持续性

B.出血量小但呈持续性

C.出血量大但呈非持续性

D.出血量小且呈非持续性

E.以上都不是

答案

参考答案：C

选择题

Chinese students usually spend _____ the students of the US studying in their free time. [ ]

A. twice as many hours as

B. as twice many hours as

C. twice hours as many as

D. as many as twice hours

单项选择题

空气SF₆含量不得超过（）ppm。

A.1000

B.500

C.100

D.50