To answer this question, we need to understand how overflow occurs when adding positive and negative numbers.
Overflow occurs when the result of an arithmetic operation exceeds the maximum value that can be represented in the given number format. In the case of adding positive and negative numbers, the overflow flag will only be set if the result is outside the range of representable values.
When adding a positive number and a negative number, the result can be positive, negative, or zero, depending on the magnitudes of the numbers. However, the overflow flag will not be set because the result will always be within the range of representable values for signed numbers.
Therefore, option D is correct because there is no overflow when adding positive and negative numbers.