In the following passage some words have been deleted. Select the most appropriate option to fill in the blank.
Curd contains several microorganisms. Of these, the bacterium, Lactobacillus (1) the formation of curd. It multiplies in milk and (2) it into curd. Bacteria are also involved in the (3)__ of cheese, pickles and many other food items. Bacteria and yeast are also helpful for the fermentation of rice idlis and dosa batter. Yeast _(4) rapidly and produces carbon dioxide during respiration. Bubbles of the gas fill the dough and increase its _____(5)____. This is the basis of the use of yeast in the baking industry for making bread, pastries and cakes.

Select the most appropriate option to fill in blank number 4.

1. A
   convert
2. B
   reproduces
3. C
   change
4. D
   leads