题目

In the United States, friendships can be close, constant, intense, generous, and real, yet fade away in a short time if circumstances change. Neither side feels hurt by this. Both may change Christmas greetings for a year or two, perhaps a few letters for a while — then no more. If the same two people meet again by chance, even years later, they pick up the friendship where it left off and are delighted. In the States, you can feel free to visit people’s homes, share their holidays, enjoy their children and their lives without fear that you are taking on a lasting obligation. Do not 显微镜下看到的像的放大倍数是目镜和物镜放大倍数的____________。A．商B．和C．差D．乘积