把工程建设定额分为劳动消耗定额、机械消牦定额、材料消耗定额的划分原则是根据( )。

A．费用性质不同

B．专业性质不同

C．物质消耗内容不同

D．用途不同

Be sure to let Tom know the truth as soon as he ______. [ ]

A. will arrive

B. was arriving

C. arrives

D. arrived