Final answer:
The sum of hexadecimal numbers is generally calculated using hexadecimal addition, not by a '16's complement' method. The '16's complement' seems to be a mix-up with the two's complement method, which is actually for binary numbers.
Step-by-step explanation:
The sum of 16's complement hexadecimal numbers such as 4F09 and D3A5 is not calculated using any of the methods listed directly. Typically, hexadecimal numbers are summed up using hexadecimal addition, where each digit is added together from right to left, carrying over as needed. However, the concept of '16's complement' isn't standard in hexadecimal arithmetic. Instead, this seems to be a confusion with the two's complement method, which is a binary number system technique used for representing signed numbers. If one is actually referring to the two's complement (in binary) and wishes to add hexadecimal numbers, they must first convert the hexadecimal numbers to binary, apply two's complement if the numbers are negative, perform the addition, and then convert back to hexadecimal if required.