Answer:
D. fatty acids.
Step-by-step explanation:
Fatty acids are present in our body and the food we eat. All fats we ingest are broken down in to fatty acids, which is stored to energetic uses. Molecules of fatty acids formed triglycerides.
As we said, the main function of fatty acids is to storage energy, so when there's no enough glucose (which is energy) to do a specific function, fatty acids take place and fulfil the task. Moreover, children are characterized for their big amount of energy and the constant movement as such, that's why fatty acids require extra servings, otherwise they won't be able to do all their normal activities which require a lot of energy.