燃气锅炉点火前,机械通风不少于(),自然通风不少于15min。
A、5min
B、10min
C、15min
D、20min
参考答案:B
— Never thought to meet you here at this time .
— [ ]
A. Glad to see you.
B. It's a small world.
C. So did I.
C. Oh, haven't you?
在感染中,标志近期感染的抗体是()
A.IgD
B.IgA
C.IgG
D.IgM
E.IgE