Which of the following is a prime number?

Explanation: A prime number is a number that is divisible only by itself and 1.

20 is divisible by 1, 2 ,4,5,10

21 is divisible by 1,3,7

22 is divisible by 1,2 ,11

19 is divisible by only itself and 1

Final Answer: Correct option is A: 19