Identify the missing number in the series: 3, 7, 15, 31, ?

A. 63

What number should come next in the series: 10, 20, 40, 80, ?

C. 160

Identify the missing number in the series: 1, 4, 9, 16, ?, 36

A. 25

What is the missing number in the series: 3, 8, 15, 24, ?, 60

B. 36

Complete the series: 3, 6, 11, 18, ?, 42.

B. 28