c
B (Black). Order of snooker balls.
dadas
The next two letters are likely C & U. There are at least 2 patterns in these letters. FIrst is the list of vowels that make up every other letter. Then the letters alternate from the ends of the alphabet. If there is a Z, a B, then a Y, then C would likely be next, and then X. But there would be whatever vowel in sequence next.
jason
bb
abcde
z
fug
The next three letters in this sequence follow by days of the week. S is sunday, m is monday t is tuesday, w is wednesday, so the next three letters are tfs because thursday friday saturday.
bb
MAMJJASO are the initial letters of the months from March through October, so the next letter in the sequence is N for November.
jj