Mud, Lake Water, or a Sewage Sample Inoculated into Mineral

Mud, lake water, or a sewage sample inoculated into mineral salts medium supplemented with an organic acid as the carbon source, lacking fixed or organic nitrogen, and incubated anoxically in the light invariably selects for

A) purple nonsulfur bacteria.
B) purple sulfur bacteria.
C) nitrifying bacteria.
D) green nonsulfur bacteria.