Question

Mark the option which contains set of prime numbers.

• A. 1, 2, 3, 5, 7
• B. 2, 5, 9, 11, 17
• C. 19, 13, 11, 7, 3
• D. 23, 29, 39, 37, 43

Answer 1

The correct option is C

19, 13, 11, 7, 3

The prime number is a number with only two factors, 1 and the number itself.

1 is not a prime number, as it has only one factor. Hence, the set 1, 2, 3, 5, 7 does not contain all prime numbers.

9 is not prime number, as it has 1, 3 and 9 as factors. Therefore, the set 2, 5, 9, 11, 17 is not correct choice.

39 has factors 1, 3, 13 and 39 hence it is not a prime number.
So the set 23, 29, 39, 37, 43 is also incorrect.

Since all the numbers the set 19, 13, 11, 7, 3 have only two factors that is 1 and itself like,
19 = 1 × 19
13 = 1 × 13
11 = 1 × 11
7 = 1 × 7
3 = 1 × 3
Hence it is the correct answer.