What is $Spirulina$?

Given below are two statements with respect to single cell protein.
Statement $I$: Single cell protein refers to the crude,or refined edible protein,extracted from pure microbial cultures or from dead or dried cell biomass.
Statement $II$: $SCP$ can be readily used as fodder for achieving fattening of calves,pigs,in breeding fish and in poultry.
In the light of the above statements,choose the correct answer from the options given below.

What is the primary benefit of consuming Single Cell Protein $(SCP)$?

In which of the following media are microorganisms $NOT$ cultured for the production of Single Cell Protein $(SCP)$?

Which organism is cultivated as a source of $SCP$?

Which of the following algae is rich in protein?