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 food rich in protein, minerals, vitamins etc.
(b) Body weight-wise the microorganisms Methylophilus methylotrophus may be able to produce several times more proteins, than the cow 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.