The agency, ______ to set and enforce health standard for American workers, has been promising a cotton dust standard for several years.

A．which is

B．which it is

C．whose job it is

D．of whose job is

下列选项中，关于混凝土灌注桩中钢筋笼质量检验标准，说法正确的有( )。

A．主筋间距的允许偏差及允许值为±10

B．主控项目的检查方法是用钢尺量

C．箍筋材质检验的允许偏差及允许值为±20

D．长度的检查方法是抽样送检

E．钢筋材质检验的允许偏差及允许值为±10