Given the following situation:

• the universal set U = {positive integers less than 20)

. X = {4, 5, 6, 7, 8)
• P = (prime numbers of U}
• O = {odd numbers of U
Which is the complement of P?

1) the even numbers of U

2) the universal set excluding the set of X

3) the positive integers greater than 20

4) the non-prime numbers of U