What letter should appear next in this sequence? F; B; H; D; J; F; L; ?

Answer 1

There are 2 sequences here interleaved with one another:
F, H, J, L ( Starting from F skipping one letter each time F, G, H, I, J, K, L..... )
&
B, D, F, (H) ( Starting from B skipping one letter each time B, C, D, E, F, G, H..... )