题目

A professor told his students to go into the city slums（贫民窟）to study the life of 200 boys． He asked them to write reports about each boy's life in the future．Every one of the students wrote, He doesn't have any hope． Twenty-five years later, another professor read about the earlier study．He told his students to find out what had happened to these boys．Of the 200 boys, 20 had moved away or died． Nobody knew what had happened to them．They tried very hard and found the other 180 people．Among them, 176 had become successful as doctors, teachers and scientists． The pro下列生活用品中不属于农产品的是A.牛奶B.饼干C.粮食D.水果