What is the best explanation for why elephants stand with a more upright posture and have relatively thicker bones than cats?

A) Cats and elephants are from different taxonomic groups and therefore differ in appearance.
B) Cats are smaller and need to run faster; therefore, they have smaller bones and a crouching posture.
C) Because they have a much greater volume, elephants require a disproportionately larger cross- sectional area of their bones than cats.
D) Cats eat meat and elephants eat plants, requiring different bodies.