Given a scientific question, generate a correct answer to it.

Ex Input:
What is the period during which humans become sexually mature called?

Ex Output:
puberty

Ex Input:
The pelvic girdle, consisting of a hip bone, serves to attach a lower limb to this?

Ex Output:
axial skeleton

Ex Input:
What term is not the same as energy, but means the energy per unit charge?

Ex Output:
voltage