---Jim is very _____about helping left—behind children.

----Oh, it is really an ______job.

A．exciting ,exciting

B．exciting ,excited

C．excited, exciting

D．excited, excited

一氧化碳和甲烷分别在空气中完全燃烧，若生成等质量的二氧化碳，则消耗的一氧化碳和甲烷的质量比是多少？