The digit in the hundredths place in the number 8.731 is 3.
To determine which digit is in the hundredths place, you count two places to the right of the decimal point. In the number 8.731, the digit 3 is in the hundredths place. The number to the left of the hundredths place is 1, which is in the tenths place. The number to the right of the hundredths place is 1, which is in the thousandths place. So, the digit 3 is the correct answer.