夹套式压力容器的内筒主要承受的压力是（）。
A.内压
B.外压
C.内压和外压
参考答案：C
____ she is not so cheerful _____ she used to be?[ ]
A. How is it that; as
B. Why is it that; what
C. Is it why; that
D. How it is that; as
某人手指不慎划破出血，一段时间后感染发炎。血液中与止血和避免发炎有关的血细胞分别是[ ]
A．血小板、血浆
B．血小板、白细胞
C．红细胞、血浆
D．白细胞、血浆
