The given sequence is a combination of two series:
I; 1st, 3rd, 5th, 7th, 9th, 11th terms ie., A, B, C, D, E, ?
II; 2nd, 4th, 6th, 8th, 10th terms ie., B, D, F, H, ?
Clearly, I consists of consecutive letters while II consists of alternate letters. So, the missing letter in I is F, while the missing letter in II is J. So the missing terms are J and F respectively.
Hence the answer is (c).