C A school bus is a kind of bus designed for student transport: carrying children and teenagers to and from school. So safety is very important. We should have the same logo on the school bus and color it yellow so that people can see it far away. People design everything on the bus to keep the students safe, such as, we can push the windows easily, the computer can ask the student to wear the seatbelt when the student sits on the seat. There is at least one teacher to look after the students on the bus. When the students get on or get off the bus, the driver should use the traffic lights to tell other cars, then the other cars can wait until the students are safe. When a school bus is on the way, we can know where it is and what happens to it on the computer. In a word, we must find ways to make sure the traffic safety is first. 56. When we design a school bus, ____ is first.