Explanation:

- Solution A: The acid to water ratio is 2:7. This means for every 9 parts of solution A, 2 parts are acid.

- Solution B: The acid to water ratio is 4:5. So for every 9 parts of solution B, 4 parts are acid.

- Mixing Ratio: Solutions A and B are mixed in the ratio of 4:3.

- Total parts of mixture = 4 (parts of A) + 3 (parts of B) = 7 parts.

- Acid in the mixture:

- From Solution A: \((4 \text{ parts of A}) \times \left(\frac{2}{9} \right) = \frac{8}{9}\).

- From Solution B: \((3 \text{ parts of B}) \times \left(\frac{4}{9} \right) = \frac{12}{9}\).

- Water in the mixture:

- From Solution A: \((4 \text{ parts of A}) \times \left(\frac{7}{9} \right) = \frac{28}{9}\).

- From Solution B: \((3 \text{ parts of B}) \times \left(\frac{5}{9} \right) = \frac{15}{9}\).

- Total Acid in mixture = \( \frac{8}{9} + \frac{12}{9} = \frac{20}{9}\).

- Total Water in mixture = \( \frac{28}{9} + \frac{15}{9} = \frac{43}{9}\).

- Resulting Ratio: Acid to Water is \(\frac{20}{9} : \frac{43}{9} = 20 : 43\).

- Correct Option: 4, 20:43