题目

Stephen used to work in a company. Unluckily, he got serious heart disease. He couldn't work for a long time. Thinking he could still do something for others, he decided to be a volunteer(志愿者) at a Children's Hospital. Stephen loved children very much. With his love, he did his job well. Sometimes he lost one of his children. They died. At that time, he would tell these sad parents that he would soon be with their children in heaven (天堂) and he would take care of them. His words seemed to help those parents   There was a girl who could not walk because of a disease. She couldn't do 4．计算：2×1，2×$\frac{1}{2}$，2×（-1），2×（-$\frac{1}{2}$）联系这类具体的数的乘法，你认为一个非0的有理数一定小于它的2倍吗？为什么？