主要用于仪表控制以及取样阀等管路中的阀门是（）。
A.节流阀
B.减压阀
C.球阀
D.旋塞阀
参考答案：A
—I wonder why he has been acting so strange these days.
—Recent pressure at work may ______ his behavior.
A．account for
B．make for
C．change for
D．stand for
Modem能够提供的最大传输速率为（）kbit/s。
A.14.4
B.28.8
C.33.6
D.56
