Why might animal hormones function differently than plant ...

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Why might animal hormones function differently than plant hormones?
A) Animal receptors are very different than plant receptors.
B) Plant cells have a cell wall that blocks passage of many hormones.
C) Plants must have more precise timing of their reproductive activities.
D) Plants are much more variable in their morphology and development than animals.
E) Animal receptors are more hydrophobic than plant receptors.

[clippers!]

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