Pigments phycocyanin and phycoerythrin are found in

Assertion: Bacteria have three basic shapes,i.e.,round,rod,spiral.
Reason: Cocci and Bacilli may form clusters or chains of a definite length.

Which of the following are symbiotic prokaryotic organisms that fix atmospheric nitrogen?

An organism that performs photosynthesis but does not release any molecular oxygen during the process is:

According to Bradley and Carr,the nitrogen fixation takes place in

Assertion $A$: Bacillus and Coccus types of bacteria are found in colonial forms.
Reason $R$: In bacteria,cells formed by cell division remain surrounded by a secreted mucilaginous substance.
Which option is correct for Assertion $A$ and Reason $R$?