The assertion is correct, as India was indeed considered suitable for cotton cultivation by the British due to its favorable climatic conditions, fertile soil, and availability of cheap labour. However, the reason, although true, does not directly explain why India was considered a suitable country for cotton cultivation. The drop in American cotton exports due to the Civil War did make Britain seek alternatives, and India was one of those alternatives, but this is not the primary reason the British found India suitable for cotton cultivation.
Conclusion:
Therefore, both the Assertion and Reason are true, but the Reason is not the direct explanation of the Assertion. Thus, the correct answer is (B).