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 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