单选题 3. It was not until then that I came to know that knowledge has come only from practice.

【正确答案】 C

【答案解析】 应改为comes。本题考查动词时态。当表示客观事实、普遍真理时，应用一般现在时。“实践出真知”为客观真理，所以应将has come改为comes。
直到那时我才意识到实践出真知。