You must your cigarette when you are at the gas station.A. put downB. put onC. put offD.

问题补充：

You must your cigarette when you are at the gas station.

A. put down

B. put on

C. put off

D. put out

答案：

A. put down

B. put on

C. put off

(答案→)D. put out

解析：考查动词短语的辨析。put down写下，put on穿上，put off脱下，put out扑灭，根据语境在加油站必须把香烟熄灭，所以选D。