So mysteriously ______ missing that many puzzles wait to be solved.

A．did Flight MH370 go

B．Flight MH370 went

C．does Flight MH370 go

D．had Flight MH370 gone

对“劳动是财富之父，土地是财富之母”这句话的正确解释是

A．劳动和土地都是价值的源泉

B．劳动创造使用价值，土地形成价值

C．劳动是创造价值的外部条件，土地是价值的真正源泉

D．劳动必须和自然物相结合才能创造出物质财富