Assertion:. River valleys are among the most densely populated areas of the world.
Reasoning: Water is the most important factor for life.

Both Assertion (A) and reasoning (R) are correct and R is the correct explanation of A.

The correct answer is option 1: Both Assertion (A) and reasoning (R) are correct and R is the correct explanation of A.

Explanation:

Assertion (A): River valleys are among the most densely populated areas of the world. This statement is true. River valleys often provide fertile land for agriculture, access to fresh water, and transportation routes, making them attractive for human settlement. Many major cities and civilizations have developed along river valleys.

Reasoning (R): Water is the most important factor for life. This statement is also true. Water is essential for drinking, agriculture, sanitation, and various economic activities. The availability of water significantly influences population density and settlement patterns.

Relationship:

The reasoning explains why river valleys are densely populated, as access to water supports life and agriculture. Therefore, both the assertion and reasoning are correct, and the reasoning correctly explains the assertion.