Arabidopsis thaliana seedlings show positive phototropism: they bend and grow toward the source of (blue) light. However, phototropism is not observed if the seedlings are treated with an auxin efflux inhibitor called NPA. Knowing that auxin stimulates elongation of the cells in the growing shoot, these observations are consistent with a model in which, in the presence of a lateral light, ...

A) auxin efflux transporter proteins become localized to the side of the cell that is facing the light source.
B) auxin efflux transporter proteins become localized to the side of the cell that is away from the light source.
C) auxin influx transporter proteins become localized to the side of the cell that is facing the light source.
D) auxin influx transporter proteins become localized to the side of the cell that is away from the light source.
E) auxin efflux transporter proteins become uniformly distributed around the cell.
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