钢结构图中用表示何种螺栓()?
A.粗制螺栓
B.精制螺栓
C.永久螺栓
D.安装螺栓
参考答案:D
一I'm sorry, I was late.
—________. [ ]
A. Not at all
B. It doesn't matter
C. Of course not
D. Don't mention it
烟草中的尼古丁对人体心血管的影响不包括( )
A.使血压升高
B.使红细胞数量增多、血液变稠
C.容易引发心脏病
D.加重了心脏负担