A pressure cooker reduces cooking time for food because:

The boiling point of water involved in cooking is increased

A pressure cooker reduces cooking time for food primarily because the boiling point of water is increased inside the cooker due to the higher pressure. In a regular cooking pot, water boils at $100$ degrees Celsius $(212$ degrees Fahrenheit$)$ at atmospheric pressure. However, when using a pressure cooker, the sealed environment allows the pressure to build up, raising the boiling point of water. The increased pressure inside the cooker allows the temperature of the boiling water to exceed $100$ degrees Celsius $(212$ degrees Fahrenheit$)$, typically reaching around $121$ to $135$ degrees Celsius $(250$ to $275$ degrees Fahrenheit$)$.

The higher boiling point achieved inside the pressure cooker results in more efficient heat transfer to the food, leading to faster cooking. The increased temperature and pressure help break down the food's structure and cook it more rapidly. This is particularly useful for tenderizing tough cuts of meat or reducing the cooking time for legumes and grains.

While options $(1)$, $(3)$, and $(4)$ describe various aspects of cooking, they do not directly explain why a pressure cooker reduces cooking time.