What Did Darwin's Experiments on Phototropism Illustrate

Multiple Choice

What did Darwin's experiments on phototropism illustrate?

A) that signals from plant roots control phototropism
B) that an opaque cap placed over a shoot tip will cause a plant to bend toward light, but will inhibit growth
C) that a translucent cap placed over a shoot tip will cause a plant to bend toward light, but will inhibit growth
D) that a translucent cap placed over a shoot tip will cause a plant to both grow and bend toward light