校车问题引起了社会各界的广泛关注。请你根据下面的提示．将下列有关乘坐校车的规定补充完整。（每空词数不限)
Here are the rules we must follow when we take the school bus.
★ Don’t                           the school bus. or you’ll miss it.
★ Please                   in line when you get on or get off the bus.
★ Don’t drop litter. Keep the bus clean and tidy. 
★ Don’t talk to the drivers. It is necessary to keep_________________
★ Don’t put your heads or your arms out of the windows.
★ Make sure it is safe to                 the street! after you get off the bus.
★ If anything unusual happens, please                              .