A student observes that it is hard to hear music underwater in a pool. They state that the sound is always muffled. They conclude that the speed of sound in water must be slower than in air. A.
The conclusion might be valid. But the information is not absolute proof.

B.
The conclusion is not valid. All sound waves travel at the same speed, not altitude.

C.
The conclusion is not valid. The speed of sound should be greater in liquids.

D.
The conclusion is correct based on properties of sound waves.