-- There is nobody here. Let's play football.

-- No, we can't. My father often tells me _______ in the street. It's dangerous.

A. to play              B. don’t play             C. not to play

DF4型内燃机车中冷器作用有（）。

A、降低增压空气温度

B、进一步提高空气密度

C、提高柴油机功率

D、增加热负荷