Which sentence contains proper punctuation?

A.
The fast, laser printer had my report ready in seconds.

B.
Everyone spent several hours studying for the difficult, algebra test.

C.
The busy, parking lot was filled with cars and trucks.

D.
No one wanted to leave the refreshing, cool pool on such a hot day.

D.

No one wanted to leave the refreshing, cool pool on such a hot day.

how do you know?