病原体在宿主机体内定期繁殖，引起感染的能力，称（）
A.感染力
B.致病力
C.传染力
D.人群易感性
E.疫区
参考答案：C
--- _____ the change of the schedule ______?
--- Oh, God! I forgot all about it. I’ll do it right now.
A．Has, been announced
B．Was, announced
C．Has, announced
D．Had, been announced
钾石灰钻井液中用（）控制其碱度。
A、NaOH
B、Fe（OH）3
C、CaCl2
D、KOH
