Explanation:

- Given: Principal = Rs20,000, Rate = 5% per annum, Compound Interest = Rs2,050.

- We are to find out the time period.

- Option 1: 2.5 years

- Calculate compound interest using the formula:

$$ A = P \left(1 + \frac{r}{100}\right)^n $$

- Here, $$ A = 20,000 + 2,050 = 22,050 $$

- Solving for n, 2.5 years gives a different interest.

- Option 2: 2 years

- Calculate the amount after 2 years:

- $$ A = 20,000 \times \left(1 + \frac{5}{100}\right)^2 $$

- $$ A = 20000 \times 1.1025 = 22050 $$

- Matches the given interest.

- Option 3: 4 years

- Solving for 4 years gives a much higher interest.

- Option 4: 3 years

- Solving for 3 years also gives a higher interest.

- Correct Answer: Option 2, 2 years