In the sequence 1, 3, 6, 10, what is the next number?

A. 15

In the series 2, 4, 8, 16, what is the next number?

C. 32

What is the next letter in the series: A, C, E, G, ?

A. H

In the sequence: B, D, F, H, ?, what comes next?

A. J

Find the next letter in the series: Z, Y, X, W, ?

A. V