Which fish gives birth to young ones?

Which of the following fins are paired in fish?

Which of the following has an endoskeleton made of cartilage?

Assertion $A$: Sharks are viviparous animals.
Reason $R$: Sharks possess mammary glands.
Which option is correct for Assertion $A$ and Reason $R$?

'Maltese cross' is found in

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