Explanation:

- The initial population of the town is 12,000.

- The population increases at a rate of 10% per annum.

- To calculate the population after 3 years, use the compound interest formula:

$$

\text{Final Population} = \text{Initial Population} \times (1 + \text{Rate})^{\text{Time}}

$$

- Plugging in the values:

$$

\text{Final Population} = 12,000 \times (1 + 0.10)^3

$$

- Simplify further:

$$

\text{Final Population} = 12,000 \times (1.1)^3 = 12,000 \times 1.331 = 15,972

$$

- So, the population after 3 years is 15,972.

Option 1: 15,972