闪蒸气的主要成分是()
A、CH4
B、H2S
C、CO2
D、H2O
参考答案:A
We have reminded him again and again, but ______ turned to be of no use.[ ]
A. which
B. that
C. it
D. what
已建立劳动关系,未同时订立书面劳动合同的,应当自用工之日起一年内订立书面劳动合同。