常温常压下，一种气态烷烃与一种气态烯烃的混和物共2升，完全燃烧后，恢复到原状况，得到2.4升二氧化碳。则该混和气体中一定含有

A．甲烷

B．乙烯

C．乙烷

D．丙烯

They have        the possible time and exact materials needed to complete the project.[ ]

A. figured out      

B. taken out      

C. picked out      

D. left out