Four options have been given, out of which three are alike in some manner and one is different. Select the number that is different from the rest.
720, 120, 24, 8, 2, 1, 1

Given: 720, 120, 24, 8, 2, 1, 1

720 ÷ 6 = 120,

120 ÷ 5 = 24,

24 ÷ 4 = 6,

6 ÷ 3 = 2,

2 ÷ 2 = 1,

1 ÷ 1 = 1,

but 8 is incorrect as 24 ÷ 4 should be 6 instead of 8.

Thus, the correct answer is (b).