Sir, I request to make more mock test of this level for GATE 2020
(Every question in this paper giving better clearity of concepts )
All statements are correct.
D is the answer.
@gmrishikumar Any set is countably infinite if you can make one-to-one correspondence of its elements with natural numbers.
In case of prime numbers, you can say that -:
1st prime = 2
2nd prime = 3
3rd prime = 5.............and so on.
Thus, they are countably infinite.