保护眼睛是常识。

Bǎohù yǎnjīng shì chángshí.

Protecting the eyes is common sense.

这是一本常识性的书籍。

Zhè shì yī běn chángshí xìng de shūjí.

This is a book of common knowledge.

吃饭前要洗手是常识。

Chīfàn qián yào xǐshǒu shì chángshí.

It's common sense to wash hands before meals.