Answer:
A
Step-by-step explanation:
To control her portion size.
Calorie intake does make sense, but you're more accurate with portion size. Given restaurants always give you way more than the average serving size you're suppose to eat; putting half of her food in a box for the next day is a much better way to control her portion size. If Eloise wants to reduce the serving size, that's exactly what I just explained. She is trying to reduce the serving size, but portion is much more important. If she's going by dietary guidelines, then D is most definitely wrong. If it was against the guidelines, the restaurant would not be allowed to serve that much food. So, option A makes the most sense.
Just in case I am wrong, make sure it isn't C!