Which microorganisms are used in the production of Single Cell Protein $(SCP)$?

Which branch is useful for cultivating a large number of microorganisms for the production of Single Cell Protein $(SCP)$?

People recovering from a long illness are advised to include the alga $Spirulina$ in their diet because it:

People recovering from a long illness are often advised to include the alga $Spirulina$ in their diet because it

The advantages of single cell proteins are:
$I$. Easy to grow
$II$. Nutrient rich
$III$. High yield
Choose the correct option.

Statement $A$: Protein-rich food produced by microorganisms is called Single Cell Protein $(SCP)$.
Reason $R$: The production of Single Cell Protein causes environmental pollution.
Which option is correct for Statement $A$ and Reason $R$?