dosa and idlii and fermented preparation of rice and black gram the fermentation is done with\tleuconstoc\tstreptococcus\tsaccharomyces\tmore than one option is correct

The correct option is 4.
The idli batter is prepared by grinding soaked rice and skinned and soaked black gram. Black gram is a legume and is rich in protein; hence it supports microbes like yeast. It is of advantage that there is yeast floating in the air all around us all the time, and some of this yeast will make its way to the sugar/starch rich batters containing sufficient amount of water for the yeast to start growing and dividing.

This yeast is known as the wild yeast. Yeast is a unicellular organism in the class of fungi. On maturing, the cell undergoes multiplication by budding and fission. This process can proceed even while the cells are afloat in the atmosphere where the available moisture helps sustenance of the life form. Thus the air around us has sufficient yeast microbes.