Principle involved: effect of pressure on boiling point

In a pressure cooker, the pressure inside the vessel is greater than atmospheric pressure.

We know that a liquid boils when its vapour pressure becomes equal to the external pressure. If the external pressure increases, the liquid must be heated to a higher temperature before it can boil.

Therefore, inside a pressure cooker, water boils at a temperature higher than $100^\circ\text{C}$.

Why does this reduce cooking time?

Food cooks faster at higher temperature because the rate of the chemical and physical changes involved in cooking increases with temperature.

So the direct reason specific to a pressure cooker is that the boiling point of water is raised, allowing cooking at a higher temperature.

Check each option

A. boiling point of water involved in cooking is increased
This is correct. Increased pressure raises the boiling point of water.

B. the higher pressure inside the cooker crushes the food material
Incorrect. The pressure does not cook food by crushing it.

C. cooking involves chemical changes helped by a rise in temperature
This statement is generally true, but it is not the specific reason for the pressure cooker effect unless we first explain that pressure increases the boiling point and hence the temperature. In an MCQ asking why a pressure cooker reduces cooking time, the best answer is the pressure-induced increase in boiling point.

D. heat is more evenly distributed in the cooking space
Incorrect. This is not the main reason.

Final answer

The correct option is: $\boxed{\text{A}}$

Comparison with stored correct answer

Stored correct answer: A
Derived answer: A
They match.