How Are Plant Stems Different from Plant Roots

How are plant stems different from plant roots?

A) Stems contain phloem and roots contain xylem.
B) Energy is only available for animals to eat in the roots.
C) Roots are just underground stems.
D) They're the same, really, since "eyes" on roots are really buds.
E) Stems provide structural support above ground, allowing the plant to grow upward toward light.