What is the next number in the series: 10, 20, 30, 40, ?

B. 50

What number should replace the question mark in the series: 3, 6, 11, 18, ?, 38

B. 26

Identify the missing term in the series: 3, 6, 11, 18, ?

A. 25

Find the missing term in the series: 1, 1, 2, 3, 5, ?, 21.

B. 13

Identify the missing number in the series: 2, 5, 10, 17, ?

B. 25