Select the number-pair from the given options where the first number is NOT related to the second number as in the given number-pair:
4 : 8

The logic followed here is:
Second number = First number × (First number ÷ 2)
Given: 4 : 8 => 4 × (4 ÷ 2) = 4 × 2 = 8

Similarly,
2 : 2 => 2 × (2 ÷ 2) = 2 × 1 = 2
3 : 9 => 3 × (3 ÷ 2) = 3 × 1.5 = 4.5 ≠ 9
6 : 18 => 6 × (6 ÷ 2) = 6 × 3 = 18

8 : 32 => 8 × (8 ÷ 2) = 8 × 4 = 32

Correct answer is (b).