Which of the following sentences is written correctly?

A.
When she talks, everyone stops what they are doing. She has the better loud voice out of everyone in the class.

B.
When she talks, everyone stops what they are doing. She has the best loud voice out of everyone in the class.

C.
When she talks, everyone stops what they are doing. She has the louder voice out of everyone in the class.

D.
When she talks, everyone stops what they are doing. She has the loudest voice out of everyone in the class.