农具的发明和改进对农业发展能起到巨大的推动作用。下图农具按其出现的先后顺序排列应该是（    ）

    I saw an accident on my way to the college three days ago.

    I was waiting for the bus at the but stop. When the bus came, I got on the bus and sat on the window side. The bus started to move. After about five minutes, the bus stopped to wait for the signal(信号灯). I looked outside and saw an old man crossing the road. There were not many people on the road. A boy was riding a motorbike very fast form my side. It seemed that he did not see the signal. When the boy took notice of the old man, he tried to slow down his motorbike but there was no time. He collided with the old man very badly. The old man was thrown far away The boy also fell down. His head hit the road but it was saved because of his helmet(头盔). Both of them lay in the pool of blood. Many people gathered(聚集) around them and gave their ideas. I got afraid because I saw the whole accident. Then a woman stopped and called the ambulance( 救护车 ). It came quickly and rushed them to hospital.

    The next day I read the newspaper. The old man died in the ambulance but the boy was saved in time. This was the most terrible accident I saw ever in my life.