Why Do Plants Tend to Store Energy in the Form

Why do plants tend to store energy in the form of starch molecules in their roots, making them good to eat?

A) By providing food for grazing animals, the plants disperse themselves to spread out their population.
B) The food is hidden underground, so fewer animals find it to eat.
C) In winter when the aboveground portion of the plant freezes and dies, it can survive until spring on the energy it's stored underground.
D) The underground energy can be brought up and used to keep the aboveground portion of the plant from freezing in the winter.
E) The energy stored underground can be used underground to pull in water and nutrients from the soil.