从A、B、C、D四个选项中选出可以填入空白处的最佳选项。
1．He________more than 5,000 English words when he entered the university at the age of 15.
A．has learned B．would have learned
C．learned D．had learned
【解析】 考查动词时态的运用。根据句子中的时间状语when he entered the university at the age of 15可知，在上大学之前学的英语单词，故用过去完成时。
【答案】 D
