题目

Once when I was facing a decision that involved high risk, I went to a friend. He looked at me for a moment, and then wrote a sentence containing the best advice I’ve ever had: Be bold and brave — and mighty (强大的) forces will come to your aid. Those words made me see clearly that when I had fallen short in the past, it was seldom because I had tried and failed. It was usually because I had let fear of failure stop me from trying at all. On the other hand, whenever I had plunged into deep water, forced by courage or circumstance, I had always been able to swim until I got my 2000年某区有15000名学生参加高考，为调查他们的数学考试情况，评卷人抽取了800名学生的数学成绩进行统计，那么下列四个判断正确的是（ ）A．每一名学生的数学成绩是个体B．15000名学生是总体C．800名考生是总体的一个样本D．上述调查是普查