易于感冒的原因是（）
A.气的推动作用减弱
B.气的温煦作用减弱
C.气的防御作用减弱
D.气的固摄作用减弱
E.气的气化作用减弱
参考答案：C
—No one answered when I phoned this morning. Where were you?
—I for teeth in the dental clinic.
A．was being treated
B．have been treated
C．was treated
D．Treated
阀门安装前，应作强度和严密性试验。试验应在每批(同牌号、同型号、同规格)数量中抽查( )，且不少于一个。
A．5%B．10%C．15%D．20%
