The cost of oil is less than _______ of gas.

A．it

B．one

C．the one

D．that

（）等主要造成汽车排放污染物。

A.内燃机内混合气燃烧

B.制动衬片的磨损

C.离合器衬片的磨损

D.轮胎摩擦磨损