第21题: [单项选择]By "held back" (Line 1) the author means" ______ ". A. made to remain in the same classes B. forced to study in the lower classes C. drawn to their studies D. prevented from advancing 参考答案:D 答案解析:本题考核学生对在具体上下文里的词组hold back的理解。根据上下文,这个词组的意思是“阻挡,阻止……的发展”,因此选项D是答案。