$(N/A)$ It takes $3-10 \ kg$ of grain to produce $1 \ kg$ of meat through animal husbandry. Therefore, shifting to a meat-based diet significantly increases the demand for cereals used as animal feed.
$(B)$ This emerging area of research is known as Single Cell Protein $(SCP)$ production.
Benefits of $SCP$:
$1$. It provides a sustainable and high-quality source of protein for human and animal nutrition.
$2$. Microbes like $Methylophilus \ methylotrophus$ and $Spirulina$ can be grown on an industrial scale using agricultural waste like molasses, starch, or animal manure.
$3$. It is rich in proteins, minerals, fats, carbohydrates, and vitamins, making it an excellent alternative to combat malnutrition and food scarcity.