If U = {1, 2, 3, . . . 20 } and S = set of prime numbers , then S =

• A. { 3, 5, 7, 11, 13,17 }
• B. { 2, 3, 5, 7, 11,13, 17, 19 }
• C. {1, 3, 5, 7, 9,11, 13, 15,17, 19 }
• D. {1, 2, 3, 5, 7,11, 13, 17 }