Assertion (A): The body breaks down complex substances in food into smaller components in the digestive system.

Reason (R): Breaking down of food into simpler substances helps in easy and efficient absorption of nutrients.

The correct option is A Both (A) and (R) are true and (R) explains (A)
The process of breaking down food into simpler substances is called digestion. Digestion helps in increasing the surface area of absorption and thus the nutrients can be efficiently absorbed by the body. Hence, reason explains assertion.