Astronauts use $.....$ as a food supplement.

The alga rich in protein is

In biotechnological studies,the alga that is exploited as a rich source of protein is

$A$: Proteins produced by microorganisms are known as Single Cell Proteins $(SCP)$.
$R$: The production of Single Cell Proteins causes environmental pollution.

Consider the following four statements $(1-4)$ and select the option that includes all the correct statements:
$(1)$ The unicellular $Spirulina$ can produce large quantities of food rich in protein,minerals,vitamins,etc.
$(2)$ $Methylophilus$ $methylotrophus$,because of its high rate of biomass production and growth,can produce $25$ tonnes of protein per day.
$(3)$ Common button mushrooms are rich in Vitamin $C$.
$(4)$ Rice varieties have been developed which are rich in calcium.

Statement $P$: Heterotrophic mushrooms are cultivated globally.
Statement $Q$: $A$ cow weighing $250 \, kg$ produces $200 \, g$ of protein per day.