Hello Shubham

For set A

Multiples of 3 are those numbers which come in table of 3

So, Multiples of 3 = 3, 6, 9, 12, 15, 18, 21, ....

∴ Set A = {3, 6, 9, 12, 15, 18, 21, ....}

For set B

Multiples of 5 are those numbers which come in table of 5

So, Multiples of 5 = 5, 10, 15, 20, 25, 30 ....

∴ Set B = {5, 10, 15, 20, 25, 30 ....}

Now,

A ∩ B = {15, 30, ... }

So, C is the correct answer.