Oxygen-rich blood from the lungs comes to the thin-walled upper chamber of the heart on the left. The left upper chamber (A) then relaxes. It then contracts and the blood is allowed to enter the next chamber (B), as it expands. When the muscular left lower chamber of heart contracts the blood is pumped out to the body via aorta.
Deoxygenated blood reaches from the body to the upper chamber on the right side of heart (C) and it expands. As this part contracts, the corresponding lower chamber (D) dilates. This transfers the blood to right ventricle, which in turn pumps it to the lungs for oxygenated.
Assertion (A): Human heart does not allow mixing of oxygen rich blood with carbon dioxide rich blood.
Reason (R): Human heart has different chambers.

Options

A. Both A and R are true and R is correct explanation of the assertion.
B. Both A and R are true but R is not the correct explanation of the assertion.
C. A is true but R is false.
D. A is false but R is true.

Answer

C

Explanation

Human heart is four chambered. It is composed of four chambers : right atrium, right ventricle, left ventricle and left atrium. The chambers are separated by a muscular wall that prevents the mixing of the blood rich in oxygen with the blood rich in carbon dioxide.