How is the carnivorous plant lifestyle suited for an existence in bogs?

A) Bogs contain rich populations of nitrogen- fixing bacteria, which provide nitrogen to the plants.
B) Bogs contain many soil- based proteins, which are a good source of nitrogen.
C) Bogs are naturally high in nitrogen, which favors the carnivorous plant lifestyle.
D) The lack of nitrogen in bogs selects for the carnivorous plant lifestyle of ingesting and digesting animals for nitrogen.