AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
(A) Both A and R are true and R is the correct explanation of A.
The left and right sides of the heart in mammals and birds are completely separated. This prevents mixing of oxygenated and deoxygenated blood, ensuring efficient oxygen supply for their high energy needs (maintaining constant body temperature).
Source: Life Processes, Section 5.4.1
The textbook explicitly states: "The separation of the right side and the left side of the heart is useful to keep oxygenated and de-oxygenated blood from mixing. Such separation allows a highly efficient supply of oxygen to the body. This is useful in animals that have high energy needs, such as birds and mammals." — so R directly and correctly explains A. Choose option (A).