I think the answer is either B or C, hope this helps! Sorry if it doesn't!
Answer:
They are killed by predators for energy
"Light reactions need light to produce organic energy molecules. They are initiated by colored pigments, mainly green colored chlorophylls. Dark reactions make use of these organic energy molecules. This reaction cycle is also called Calvin Benison Cycle, and it occurs in the stroma."
Because they all have something to do with animals ad what they eat.