--Susan's parents have bought -a large house with a swimming pool in Paris.

--It        be very expensive.

A．can't

B．can

C．mustn't

D．must

在常压和120℃时，乙醇蒸气和乙烯体积共VL，完全燃烧时，需要相同条件下的氧气3VL，则混合气体中乙醇蒸气和乙烯的体积比为[ ]

A．1:1

B．1:2

C．2:1

D．任意比