According to modern ideas about phototropism in plants, A) light ...

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According to modern ideas about phototropism in plants,
A) light causes auxin to accumulate on the shaded side of a plant stem.
B) auxin indirectly inhibits elongation of plant stem cells.
C) auxin is produced by the apical meristem of the coleoptile and moves downward.
D) all hormones move downward via the xylem.
E) cytokinins are more directly involved than auxins

[clippers!]

I chose A and got the answer, hope that helps.