测量Φ30～50mm滑阀的间隙可用：（）。
A.游标卡尺
B.内径千分尺和外径千分尺
C.内径量表和外径千分尺
参考答案：C
It is generally believed that constant reading and comprehending can ______ our mental ability of comprehension while physical exercise can help build up our body.
A．stress
B．effect
C．strengthen
D．decide
试述神经衰弱的主要临床表现。
