に ｖｓ が in the following sentence

[Fociis]

Be quiet in the classroom.

教室では静か に しなさい。

Why に and not が? What particular function does the に particle play in this sentence?

 

[Glenn]

〜にする is like "make something ~." You can use it with nouns and -na adjectives. To use it with i-adjectives, you have to make them into an adverb first, like when you put them before なる.