Select the number that can replace the question mark (?) in the following series.
1, 2, 6, 24, 120, ?

Correct option is C

Let's analyze the given series:
1, 2, 6, 24, 120, ?
Observe the pattern:
1=1!
2=2!
6=3!
24=4!
120=5!
It is clear that each number in the series is the factorial of a consecutive integer:
1!=1
2!=2
3!=6
4!=24
5!=120
Following this pattern, the next number should be the factorial of 6:
6!=6×5×4×3×2×1=720
Answer: C) 720​

Alternative method:

The logic followed here is :-  

Hence, the correct answer is (c).