When grown in a greenhouse, the leaves of Aloe nobilis are green. When found in the desert in the wild, however, the leaves are often red. What BEST explains this observation? A.
The environment affects the expression of A. nobilis genes.

B.
The sun changes the color of chlorophyll pigments.

C.
The plant uses red pigments for photosynthesis.

D.
The leaves become infected with a red parasite.