The answer is 4) 140.
If we closely examine the pattern of the series, we see that after a number is subtracted by a value, it is multiplied by the same value, and then it moves on to the next natural number.
- 10 - 2 = 8
- 8 × 2 = 16
- 16 - 3 = 13
- 13 × 3 = 39
- 39 - 4 = 35
The next step, according to the pattern, would be to multiply 4.
