As a great teacher,Confucius said all should go to school （ ） they could and wanted to learn.A
if B,before C,after D,since
答案貌似选A.
我想问的是，IF 引导的条件状语从句 不都一般用一般现在时吗，本题IF后面用过去式，是否可行？请回答我这个问题。