单选题严禁携带充气气球进站，译成英文应该是（）。

A、 No balloons are allowed in metro.
B、 Please don' t squat, it is dangerous.
C、 All passengers, please be careful and stay back.
D、 Please stand behind the yellow safety line while waiting for the train.

【正确答案】 A

【答案解析】