Before you board on the plane,you should switch off your mobilephone. 在你登机之前,你应该关掉手机。 When you're on the plane,you must make sure that the mobilephone is power off. 你在飞机上时必须确保手机是关机的。 when you're at the automobile gasoline filling station,you must switch off off your mobilephone. 你在加油站的时候,必须关掉手机。 When it's going to thunder,you'd better switch your mobilephone. 如果天快打雷了,你最好关掉手机。 When you're going to bed and want to put your mobilephone beside you,you'd better switch it off. 你在上床睡觉并且想把手机放在身边时最好关掉手机。
In some places for example, aircraft, gas stations, when the thunder, etc you should turn off your phone.In case,something terrible happens. 在飞机上,加油站,打雷的时候要关掉手机,以防意外