a, e, i, __,u These all are vowels. So missing vowel is 'o'

2, 4, 7, 12, 19,---- Each no + prime no =next number +2, +3, +5, +7, next prime no is +11So ans is 19+11=30

1,2,4,7,11,16,-------

+1, +2, +3, +4, +5,

So the ans is 16+6=22

a, c, e, g, i, __one letter is skiping

So the ans is K

Maths is very very EASY.