Choose the missing terms out of the given alternatives :S-4, F-6, H-8, J-10, ?, ?

The correct answer is B. L-12, M-14.

The sequence is $2n$, where $n$ is the number of the letter in the alphabet. So, the next two terms are $L-12$ and $M-14$.

A. K-12, M-13 is incorrect because $K$ is the 11th letter of the alphabet, not the 12th. C. L-12, N-14 is incorrect because $N$ is the 14th letter of the alphabet, not the 13th.