In Their Experiment with Grass Coleoptiles, Charles and Francis Darwin

In their experiment with grass coleoptiles, Charles and Francis Darwin observed that the photoreceptor was _______, and the bending took place _______.

A) in the tip; also at the tip
B) below the tip; also below the tip
C) in the tip; below the tip
D) below the tip; throughout the coleoptile
E) in the tip; throughout the coleoptile