The Darwins' Experiments on Phototropism in Seedlings of a Grass

The Darwins' experiments on phototropism in seedlings of a grass plant

A) established that the base of the coleoptile contained the photoreceptor for phototropism.
B) led to the hypothesis that there exists a growth-promoting substance in the coleoptile.
C) showed that the growing region of the coleoptile and the light-sensing area were the same.
D) showed that the tip of the coleoptile was not required for the phototrophic response.
E) showed that light has no effect on plant development.