Which Conclusion Can Be Drawn from Brewer's Experiments on Pitcher

Which conclusion can be drawn from Brewer's experiments on pitcher plants?

A) Competition for light is an important factor in their competition with noncarnivorous neighbors.
B) Competition for nitrogen is an important factor in their competition with noncarnivorous neighbors.
C) The plants were at a particular disadvantage when noncarnivorous neighbors were left intact and the pitchers were starved.
D) Pitcher plants gained biomass when neighbors were present and prey was absent.