阅读理解。
A taxi hit a truck. A policeman spoke to the taxi driver and to the truck driver. He also spoke to Tom. He was a witness (目击者). This is what they said.
TRUCK DRIVER: I was driving from the airport to Newton. A car crossed the road, so I slowed down. I did not stop. A taxi hit the back of my truck. Nobody was seriously hurt but both cars were damaged（受损害）.
TAXI DRIVER: I was driving behind a truck a few kilometers from Newton. The truck stopped suddenly. The driver did not give me a warning (警告). I was driving very slowly. I could not pass the truck because there were two cars coming near from Newton. My taxi hit the truck, and some glass cut my left hand.
TOM: I was watching the traffic about a kilometer from the airport. A truck was going to Newton. It was not going very quickly. There was a taxi about two hundred meters behind the truck. It was going fast. When the truck slowed down, the taxi hit it. The taxi driver was not looking at the truck. He was looking out of the window at something. My friend saw the accident, too.
Tom's friend spoke to the policeman and agreed with Tom.
、斥力
及引力与斥力的合力F随分子间距离
的变化情况，下列说法中正确的是（）