单选题：Earthquake　　How does an earthquake start?　　What makes an ear

Earthquake　　How does an earthquake start?
　　What makes an earthquake happen? The rock of the earth's crust (地壳) may have a'fault', a kind of break in the surface. The blocks which make up the earth move, and sometimes this may cause the sides of the fault to move up and down or lengthways (纵向地) against each other. When one piece of rock starts to rub on another with great force a lot of energy is used. This energy is changed into vibrations (振动) and it is these vibrations that we feel as an earthquake. The vibrations can travel thousands of kilometers and so an earthquake in Turkey may be felt in Greece.
　　What to do during an earthquake?
　　At school
　　As soon as the earthquake starts, students should get under the desks immediately and wait until the teacher tells them it is safe to come out. The teacher should, at the same time, go immediately to the teacher's desk, get underneath (在......下面) it and stay there till the danger is over. Students must not argue with the teacher or question instructions.
　　As soon as the tremors (震动) stop, all students should walk towards the exit and go　straight to the school playground or any open space such as a square or a park.
　　They　must wait there until the teacher tells them it is safe to go.
　　At home
　　If you are at home when the earthquake occurs, get immediately under the table in the living room or kitchen. Choose the biggest and strongest table you can find. You must not go anywhere near the window and don't go out onto the balcony (阳台). Once the tremors have stopped, you can come out from under the table but you must leave the building straight away. You should walk down the stairs and should not use the lift - there may be a power cut as a result of the earthquake and you could find yourself trapped inside the lift for hours.
　　In the street
　　If you are in the street when the earthquake takes place, do not stand near buildings,fences or walls - move away as quickly as possible and try to find a large open space to wait in. Standing under trees could also be dangerous.People knew long ago how an earthquake starts. A．Right
B．Wrong
C．Not mentioned