Which fins are paired in fishes?

Which fish,caught in South Africa in $1938$,was thought to be extinct?

In which of the following fishes is the dorsal fin modified into a sucker?

Which of the following is a characteristic of cartilaginous fishes $(Chondrichthyes)$?

Teeth in $Chondrichthyes$ are modified:

Which of the following statements are not true about shark?
$a$. The skin is tough and covered with placoid scales
$b$. They possess a swim bladder which regulates buoyancy
$c$. The tail of shark is heterocercal
$d$. Ampulla of Lorenzini present in the snout of shark is a thermoreceptor.
$e$. It has five pairs of gill slits covered by operculum