Green manuring enhances crop yield by

In India, the most commonly used pesticide $BHC$  is

Consider the following four statements $(A-D)$ and select the option which includes all the correct ones only.

$(A)$ Single cell Spirulina can produce large quantities of food rich in protein, minerals, vitamins, etc.

$(B)$ Body weight­wise the microorganism Methylophilus methylotrophus may be able to produce several times more proteins than the cows per day.

$(C)$ Common button mushrooms are a very rich source of vitamin $C$.

$(D)$ A rice variety has been developed which is very rich in calcium.

In cattle, these are help in the digestion ofcellulose.

Penicillin is obtained from