Explanation:

- Let's analyze the series: 18, 19, 23, 31, 48, 73.

- Observe the differences between consecutive numbers:

- 19 - 18 = 1

- 23 - 19 = 4

- 31 - 23 = 8

- 48 - 31 = 17

- 73 - 48 = 25

- A pattern isn't immediately clear, but upon closer inspection:

- Differences are nearly doubling each step: 1, 4, 8, 17, 25.

- Ideally, if following a pattern, the differences seem inconsistent.

Based on analysis:

- Option 2: 31 doesn't fit well because the doubling pattern is broken here.

- The probable correct series would be: 18, 19, 23, and then it might have jumped directly to a number fitting a multiplication pattern.

Correct Answer: Option 2, 31.