Which of the following is added to increase the shelf life of milk ?

Correct option is C

The correct answer is pasteurization.
In the context of increasing the shelf life of milk, both Sodium Bicarbonate and Lactic Acid play roles, albeit in different ways.
Sodium Bicarbonate (NaHCO₃), also known as baking soda, is added to milk to neutralize the acidity. This slows down the souring process by reducing the growth of lactic acid-producing bacteria. By keeping the milk less acidic, sodium bicarbonate helps prolong its freshness.
Lactic Acid, on the other hand, may seem counterintuitive, but it is actually used in some dairy processes. For instance, in the production of longer-lasting dairy products like certain cheeses and yogurt, controlled amounts of lactic acid are introduced through bacterial cultures. These cultures convert lactose in the milk into lactic acid, which acts as a preservative by lowering the pH and creating an environment less hospitable to harmful bacteria.
Therefore, both Sodium Bicarbonate and Lactic Acid, in different contexts, contribute to the increased shelf life of milk and milk products.