The series B, C, E, G, K is built on the places its letters occupy in the alphabet. What is its next letter?

The places of the letters are 2, 3, 5, 7, 11 — the prime numbers in turn. The next prime is 13, and the thirteenth letter is M. The gaps run 1, 2, 2, 4, which tempts one to take the next gap as 4 and answer O, or to take it as 1 and answer L. N, at place 14, is what you get by adding 3 to 11 on the guess that the gaps grow by one each time.