他的信很难读，因为没有使用任何标点符号。

His letter was difficult to read because it had no ___punctuation.

我们的英语老师正在向全班讲解标点符号的规则。

Our English teacher is explaining the rules of ___punctuation to the class.

正确的标点符号对于清晰的写作非常重要。

Correct ___punctuation is very important for clear writing.