The large holes in 'Swiss Cheese' are due to:

The correct answer is Option (3) → Production of large amount of CO₂

Option (1) Production of large amount of O₂ — Incorrect. The bacteria do not give off oxygen.

Option (2) Citric acid — Incorrect. Citric acid is made by Aspergillus niger; it is not a gas and makes no holes.

Option (3) Production of large amount of CO₂ — Correct. The bacterium Propionibacterium sharmanii produces it inside the cheese.

Option (4) Ethyl alcohol — Incorrect. Alcohol is a liquid, made by yeast in brewing.

NCERT Extract:
Microbes in Household Products – “… Different varieties of cheese are known by their characteristic texture, flavour and taste, the specificity coming from the microbes used. For example, the large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium named Propionibacterium sharmanii.”