Please choose the right answer

题目

Please choose the right answer
He _____ more than 5,000 English words when he entered the universityat yhe age of 15.
A、has learned
B、would have learned
C、learned
D、had learned

答案

D
当他在15岁进入大学时,他已经学了超过5000个英语单词.
entered the university 在过去,那么学习英语单词就是在过去的过去,所以用过去完成时,即D