A Researcher Is Studying the Distribution of Auxin in Roots

A researcher is studying the distribution of auxin in roots and stems exposed to sunlight. He notices that more auxin collects in the sides of stems and roots that are not exposed to light; however, the effects of this distribution are very different. Why?

A) Auxin prevents cell elongation in the shaded cells of stems.
B) Auxin (via ethylene) promotes cell elongation in the shaded cells of roots.
C) Auxin (via ethylene) prevents cell elongation in the shaded cells of roots.
D) Auxin promotes cell elongation in the shaded cells of stems.