当吊钩挂绳处截面磨损量超过原高度的10%应采取()。
A、焊补
B、校正
C、补强
D、更换
参考答案:D
If you want to get good grades, ____________, you should listen to the teacher _________ in class.
A.at first; careful
B.first of all; carefully
C.for the first time; careful
D.first of; carefully
下列哪些属于化学致癌物质?()
A.3,4-苯并芘
B.组胺
C.缓激肽
D.联苯胺
E.硝酸钠