Express the fraction 0.724 as a mixed number.

To convert a decimal to a mixed number, you need to know that the whole number will be on the left side of a decimal and the fraction will be on the right. The "2" in choice A is the whole number and the "5/8" is the fraction. Option B is incorrect because it has a fraction larger than one, which is not possible in a mixed number. Option C has a fraction with a denominator larger than the numerator, which is also not possible. Option D has the whole number and fraction switched, with 9 as the fraction and 1/6 as the whole number, which is incorrect. Therefore, option A is the correct answer as it correctly expresses 0.724 as a mixed number.