Question

Passengers .....

open the door when the train is moving.
must
mustn't
should
shouldn't
​

Answer 1

should not

Step-by-step explanation:

the above sentence is a type of advice for the passengers and we use should/shoud not to give some sort of advice

Answer 2

shouldn't

Step-by-step explanation:

that is correct grammer because they shouldn't be opening the doors when the train is moving