Question

which sentence uses this meaning of vacuum?
vacuum noun a space that is completely empty
the chemist pumped the air out of the small glass chamber and turned it into a vacuum.
guests will be here in five minutes, so wed better vacuum quickly!

Explanation:

We need to find the sentence where "vacuum" means "a space that is completely empty". In the first sentence, the chemist pumps air out of a chamber, making it a space with no air (completely empty), so "vacuum" here is a noun meaning an empty space. In the second sentence, "vacuum" is a verb meaning to clean with a vacuum cleaner, which doesn't match the given meaning.

Answer:

The chemist pumped the air out of the small glass chamber and turned it into a vacuum.