By adjusting the volume of gas in ____, a ray-finned fish can change its buoyancy so that it remains suspended at the desired depth.

A) lungs
B) gills
C) bladder
D) swim bladder
E) buoyancy sac

The swim bladder is a gas-filled sac located in the abdominal cavity of ray-finned fish that helps them control buoyancy. By adjusting the volume of gas in the swim bladder, fish can change their buoyancy and remain suspended at a desired depth. Lungs are not present in ray-finned fish, and gills are used for respiration, not buoyancy control. A buoyancy sac is not a recognized anatomical structure in fish.