Legionella Pneumophila Is an Opportunistic Pathogen That

Legionella pneumophila is an opportunistic pathogen that

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