Bad Day at the Gym

A Japanese exchange student sat in a science classroom, totally stumped at a
question on the final exam.
The question asked: "Give four advantages of breast milk."
What to write? He sighed, thinking he could not use personal experience.
Suddenly, he smiled, remembering some things he has overheard his mother say. He
wrote:
1. No need to boil.
2. Never goes sour.
3. Available whenever necessary.
He still needed a fourth answer. He tried to put himself in the place of a
child, but that didn't work. Suddenly, he smiled again. He wrote as the final
answer:
4. Available in attractive containers of varying sizes.
He sat back, considering how proud his friends would be for their genius
friend who lived overseas.