–You speak very good Chinese.
--Thanks. I it for 4 years before I came to China.
A. studied
B. study
C. was studying
D. had studied
网友回答
A. studied
B. study
C. was studying
(答案→)D. had studied
解析：本题回答语的含义是自从我来到中国以前，我学习英语已经学了4年，从句为过去时，主句也应该用过去时的一种，本题的主句表示的是做某事的时间长度，用完成时，故本题的空格处用过去完成时，结构为had+过去分词，故本题选D。