What is the next number in the series: 3, 6, 11, 18, ?

B. 25

M, O, Q, S, ?

B. T

Find the missing number in the series: 5, 10, 20, 40, ?

A. 80

What is the next letter in the series: M, N, O, P, ?

A. Q

What is the next letter in the series: B, E, I, N, ?

A. R