The main ingredient of South Indian dishes like idli and dosa is

Which of the following converts milk into curd and increases the amount of vitamin $B_{12}$?

Which of the following microbes is used for the ripening of Swiss cheese?

Curding of milk takes place by

The microorganism that converts milk into curd is ..........

Which of the following food items are produced through fermentation by the microorganisms?
$(I)$ Idli $(II)$ Dosa
$(III)$ Toddy $(IV)$ Cheese