Question

put a check by all the prime numbers.
5
12
13
17
19
21
none of the above

Explanation:

Step1: Recall prime number definition

A prime number is a number greater than 1 that has no positive divisors other than 1 and itself.

Step2: Check each number

• For 5: Divisors are 1 and 5. So prime.
• For 12: Divisors include 2, 3, 4, 6. Not prime.
• For 13: Divisors are 1 and 13. Prime.
• For 17: Divisors are 1 and 17. Prime.
• For 19: Divisors are 1 and 19. Prime.
• For 21: Divisors include 3, 7. Not prime.
• "None of the above" is incorrect as there are primes.

Answer:

The prime numbers are 5, 13, 17, 19. So the checkboxes for 5, 13, 17, 19 should be checked. In terms of the options (with their identifiers and text as per the table rows):

• The checkbox for "5" (first row)
• The checkbox for "13" (third row)
• The checkbox for "17" (fourth row)
• The checkbox for "19" (fifth row)