病毒的结构是由如下哪两种基本成分组成的( )
A．核酸和包膜B．壳膜和核酸C．蛋白质和核酸D．包膜和壳膜E．壳膜和核衣壳
参考答案：C
----What did you see on the large farm last Sunday?
----Oh, I saw about three ________ hens and _________ of eggs.
A．hundred; hundreds
B．hundreds; thousands
C．thousands; thousand
D．hundred; thousand
胃窦部pH达到何值G细胞分泌受抑制（）
A.<1.0
B.<1.5
C.<2.0
D.<2.5
E.<3.0
