Multiple choice

Most fishes do not sink in water because of the presence of

  1. air sinuses

  2. buoyant scales on the body

  3. swim bladder

  4. swimmers

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Most bony fish possess a swim bladder (also called air bladder) - a gas-filled organ that allows them to regulate buoyancy and maintain depth without expending energy. By adjusting the gas volume, fish can achieve neutral buoyancy. Cartilaginous fish like sharks lack this organ and must swim constantly to avoid sinking.