Why might kipling have used india as a setting for his novel kim?

Rudyard Kipling was interested in imperialism and colonialism, especially the Great Game between Great Britain and Russia, which was a scramble for influence in central Asia. India was a setting that captured these dynamics, and was Britain's greatest foothold in the region.
India was also an ideal setting to illustrate the impact of imperialism on both the occupier and the occupied territory, and to explore the challenges that both face. 

A. cause and effect is the correct answer