Q. Which class of fishes lacks an operculum and air bladder and must swim constantly to avoid sinking?
A) Osteichthyes
B) Amphibia
C) Chondrichthyes
D) Reptilia
Explanation
Cartilaginous fishes have separate gill slits without operculum and no air bladder. Bony fishes have an operculum and an air bladder that regulates buoyancy.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.