Assertion (A): The Civil War cost more American lives than any other war in history.

Reason (R): The Civil War was fought between the industrialised northern states and the agricultural southern states of America.

1. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
2. Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
3. Assertion (A) is true but Reason (R) is false.
4. Assertion (A) is false but Reason (R) is true.

Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).

Explanation — The Civil War resulted in more American deaths than any other war because of its scale and intensity, not merely because of the differences between the North and South. While it is true that the war was fought between the industrialized northern states and the agricultural southern states, this economic and cultural difference explains why the war happened, not why it was so deadly.