Multiple choice general knowledge math & puzzles SEQUENCE 2:7::11:? 17 15 19 21 Reveal answer Fill a bubble to check yourself C Correct answer Explanation The sequence follows prime numbers. 2 and 7 are prime numbers (skipping 3 and 5). Following 11, the next prime numbers are 13 and 17; skipping those leads to 19. Alternatively, 2*2+3=7 and 11*2-3=19 is less consistent.