To which habitat is a fish adapted?

The presence or absence of which of the following is used to distinguish between bony fishes $(Osteichthyes)$ and cartilaginous fishes $(Chondrichthyes)$?

Select the set of fishes which belong to the class Osteichthyes:

Fishes having a swim bladder,which does not have direct communication with the exterior and where the resorbent and secretory parts are not sharply separated from one another,are called:

Which one is a true fish?

Which group of organisms is characterized by the presence of scales,fins,and an aquatic mode of life?