Assertion (A) : Arteries have thick and elastic walls as compared to veins.

Reason (R) : The pressure of blood flow in arteries is low as compared to veins.

The correct option is (A) is true and (R) is false.

Step-by-step Explanation:

1. Analysis of Assertion (A):
Arteries carry blood away from the heart to various organs of the body. Since the heart pumps blood forcefully into the arteries, the blood flows under high pressure. To withstand this high pressure without rupturing, arteries have thick, elastic walls. Veins, on the other hand, carry blood back to the heart under much lower pressure, so they have thinner walls. Therefore, Assertion (A) is true.

2. Analysis of Reason (R):
The pressure of blood flow in arteries is actually much higher than that in veins, not low. Blood is pumped directly into the arteries by the ventricular contraction of the heart, resulting in rapid and high-pressure flow. Hence, Reason (R) is false.

Conclusion:
Assertion (A) is a correct statement, while Reason (R) is an incorrect statement. Thus, the correct choice is (A) is true and (R) is false.