Concept:
The Northern Plains of India are among the most fertile and densely populated regions of the country.
They are formed by the deposition of alluvium carried by major river systems.
Step 1: Examine Assertion A.
The Northern Plains are formed by the river basins of:
• Indus
• Ganga
• Brahmaputra
These rivers and their tributaries deposit fertile alluvial soil over vast areas.
Therefore, Assertion A is correct.
Step 2: Examine Reason R.
Reason R states that these plains are among the least populated regions of India.
This statement is incorrect.
In reality, the Northern Plains are:
• Highly fertile
• Rich in water resources
• Suitable for agriculture
• Densely populated
Major cities and agricultural activities are concentrated in these plains.
Thus, Reason R is false.
Step 3: Determine the relationship between A and R.
Since:
• Assertion A is correct
• Reason R is incorrect
the correct option is:
\[
\text{A is correct but R is not correct}
\]
Step 4: Conclusion.
Therefore, the correct answer is:
\[
\boxed{\text{A is correct but R is not correct}}
\]