To round to 3 decimal places, look at the digit in the 4th decimal place.<br><br>&bull; 499.9999 → the 3rd decimal digit is 9, the 4th decimal digit is 9<br>&bull; The 4th decimal digit is 9, which is 5 or more, so we round up<br>&bull; Rounding 9 up causes a cascade: 499.9999 → 500.000<br>&bull; As 3 decimal places, this is 500.000<br><br>Option D: 500.000 is correct.<br>Final Answer: D: 500.000