It was not until then that I came to know that knowledge only from practice.A. had come

问题补充：

It was not until then that I came to know that knowledge only from practice.

A. had come

B. has come

C. came

D. comes

答案：

A. had come

B. has come

C. came

(答案→)D. comes

解析：主句虽然是过去时态，但从句所说明的是不受时间限制的真理或事实，名词性从句的谓语动词仍然用一般现在时。又如:He said Asia is the largest continent.