Which one of the is not a prime number

- Which one of the following is not a prime number
- Which of the is not a prime number
- Which of the following is not a prime number
- Which of the given is not a prime number
- Which of the following numbers is not a prime number
- Which one of the following is not a prime number 61 71 91
- Which one of the following is not a prime number 31 61 91
- Which one of the following is not a prime number answer
- Which one of the following numbers is not a prime number
- Which of the following is not a prime number 31 41 51 and 61
- Which of the following is not a prime number 31 61 71 and 91
- Which of the following is not a prime number 2 3 4 5
- Which of the following is not a prime number 2 5 8 11
- Which of the following is not a prime number 1 2 3 5