How Does a Swim Bladder Help the Ray- Finned Fishes

How does a swim bladder help the ray- finned fishes maintain buoyancy?

A) Gas is removed from the bladder as the fish's depth increases.
B) It removes water from the digestive tract.
C) Gas is added to the bladder as the fish's depth increases.
D) It removes oxygen from the water and stores it.
E) It adds and removes salt from the water stored in the bladder, which changes its density and, thus, its buoyancy.