Explanation:

To solve this, we first need to find the number of females in town C in 2019:

- Town C: The difference between males and females = 40,000.

- Ratio of males to females = 11:3.

- Assume males = 11x and females = 3x.

- 11x - 3x = 40,000 ? 8x = 40,000 ? x = 5,000.

- Females in town C = 3x = 15,000.

Now calculate the number of males in town B in 2020:

- Males in town B (2020) = 80% more than females in town C (2019).

- 80% of 15,000 = 12,000 ? 15,000 + 12,000 = 27,000 males in town B (2020).

Determine the increase in town B from 2019 to 2020:

- Males in town B (2019) = 6x (difference = 20,000; 6x - x = 20,000) ? x = 4,000.

- Males in town B (2019) = 6x = 24,000.

- Increase = 27,000 - 24,000 = 3,000.

Calculate the percentage increase:

- Percentage increase = (3,000/24,000) * 100 = 12.5%.

Thus, the correct option is:

Option: 1, 12.5