D and A I believe not sure though
Food and Drug Administration and <span>Centers for Disease Control and Prevention </span>
Well because it is the amount that the nutritional facts are given on, say you buy a box of donuts, and it says 80 calories that could be for a 2 donuts for 1 for the whole package but knowing the serving size you can base how much you eat etc
If you find this out let me know
