Correct Answer - B
Oscillatoria is a photosynthetic cyanobacterium. In this , during photosynthesis , water is electron donor and oxygen is a by product , i.e., oxygenic photosynthesis occurs.
Rhodospirllum and Chlorobium are anoxygenic photosynthetic, purple non-sulphur and green - sulphur bacteria, anoxygenic photosynthetic.
