Legionella pneumophila is an opportunistic pathogen that

A) is part of the microbiome of the lower respiratory system.
B) is part of the microbiota of the nasal cavity which occasionally invades the lungs.
C) survives in the environment as an intracellular parasite of a protozoan.
D) is capable of forming endospores.
E) is a disease of birds transmissible to humans.