It has been five years I came to this school.for B. since C. whether D. when

问题补充：

It has been five years I came to this school.

for B. since C. whether D. when

答案：

解析：本题的含义是自从我来到这所学校以来已经有5年了，since可引导时间状语从句，表示自从……以来，故本题选B。