预防苯中毒的措施中,下列哪项是根本性措施()
A.用无毒或低毒物质代替苯
B.加强个人防护
C.车间空气定期监测
D.通风排毒
E.就业前和定期体检
参考答案:A
——Excuse me, Professor Smith, I was wondering if I could leave a quarter earlier today.
——____.
A.Nothing the matter.
B.Sure, go ahead
C.Oh, why not?
D.No trouble at all
简述综合实践活动的性质和特点。