Tansley's Experiments with Bedstraw (Galium) Showed That When Two Closely

Tansley's experiments with bedstraw (Galium) showed that when two closely related species of bedstraw are grown together,

A) one is always the superior competitor regardless of habitat.
B) bedstraw in its preferred soil type is always the superior competitor.
C) bedstraw in its preferred soil type is the better competitor for soil nitrogen.
D) one was a better competitor for light and the other for water, depending on soil type.