to get from 15 to 12 you subtract 3
to get from 12 to 17 you add 5
to get from 17 to 14 you subtract 3
to get from 14 to 19 you add 5
so, based on this pattern you can assume that you can get the next number by subtracting 3 from 19. so that means you'd do 19-3 and you would get 16 as your answer.
your answer is C.16
Hope this helps :)
