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

A. 8

What number should replace the question mark in the series: 12, 24, 48, ?, 192?

A. 96

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

A. 27

What is the missing number in the series: 3, 6, 12, 24, ?

B. 48

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

D. 80