Explanation:

- The ratio of A's age to B's age is 4:3.

- Let A's age be 4x and B's age be 3x.

- The age difference between A and B is 4 years: \(4x - 3x = 4\).

- Solving for x gives x = 4.

- So, A's age is 16 years, and B's age is 12 years.

- C is 4 years younger than B, making C's age \(12 - 4 = 8\) years.

- 10 years later, C will be \(8 + 10 = 18\) years old.

- Correct Option: 3, 18 years