理解语法规则对于学习一门语言至关重要。

Understanding the ___rules of grammar is essential for learning a language.

我们做了一个关于动词时态和语法规则的小测验。

We had a short test on verb tenses and grammar ___rules.

数学中的一条基本规则是，你不能除以零。

One basic ___rule in mathematics is that you cannot divide by zero.