The puffed-up dough of dosa and idli is due to _________.

• A

  Fermentation by bacteria and production of ${\mathrm{O}}_2$.

• B

  Hydrolysis by bacteria and production of ${\mathrm{CO}}_2$.

• C

  Fermentation by bacteria and production of ${\mathrm{CO}}_2$.

• D

  Hydrolysis by bacteria and production of ${\mathrm{O}}_2$.