NH₃和Cl₂可快速反应：2NH₃+3Cl₂ →N₂+6HCl 。有100LNH₃和Cl₂混合气体，充分反应后的混合气体中N₂占混合气体的1/7，则N₂的物质的量为（标准状况下数据）

A．0.263 mol

B．0.483 mol

C．0.663 mol

D．0.893 mol

It sounds like something is wrong with the car’s engine. ______ , we’d better take it to the garage immediately.

A．Otherwise

B．If not

C．If possible

D．If so