Explanation

Four years ago, the average age of A, B, and C was 25 years.

This means that the total age of A, B, and C four years ago was 25 x 3 = 75 years.

Since then, all three have aged 4 years, so their total age now is 75 + 4 + 4 + 4 = 87 years.

Five years ago, the average age of B and C was 20 years.

This means that the total age of B and C five years ago was 20 x 2 = 40 years.

Since then, both B and C have aged 5 years, so their total age now is 40 + 5 + 5 = 50 years.

Now, we know that the total age of A, B, and C is 87 years, and the total age of B and C is 50 years.

So, A's current age is 87 - 50 = 37 years.

The correct answer is: 37 years