阅读理解
阅读下列短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项。
A
Years ago a John Hopkin’s professor gave a group of graduate students this task: Go to the slums (贫民窟). Take 200 boys, between the ages of 12 and 16, and research into their background and environment. Then predict their chances for the future.
The students, after consulting social statistics, talking to the boys, and compiling (汇编) much data, concluded that 90 percent of the boys would spend some time in prison.
Twenty-five years later another group of graduate students was given the job of testing the prediction. They went back to the same area. Some of the boys — by then men — were still there, a few had died, some had moved
