单项选择题

A．

B．

C．

D．

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单项选择题

对于同样直径和压力的容器，采用平板封头的厚度最小（）

A．对
B．错

单项选择题

which is WRONG about small intestine villi: A.
formed by mucosa and submucosa B.
simple columnar epithelium C.
goblet cells can be exit D.
typically structures for small intestine E.
increase the surface area