Final answer:
To add moments together, you add them algebraically, considering their direction and magnitude, treating them as vectors that can have the same or opposite directions.
Step-by-step explanation:
When you are trying to add moments together, you must add them algebraically. This means that you treat each moment as a vector with both magnitude and direction. If the moments are acting in a straight line (for example, some acting to the left and some to the right), you consider their direction while adding them.
If the moments have the same direction, you add their magnitudes directly; if they have opposite directions, you subtract one moment's magnitude from the other's. Therefore, the correct answer to how you add moments together is D) Add them algebraically.