How many words have you learned you began to learn English?A. forB. ifC. beforeD. since

问题补充：

How many words have you learned you began to learn English?

A. for

B. if

C. before

D. since

答案：

A. for

B. if

(答案→)C. before

D. since

解析：for为了，对于；if是否，如果；before在……之前；since自从……以来。句意：在你开始学英语之前，你已经学会了多少单词？结合语境可知选C。