Well, you are asking on Yahoo Answers. Beggers cannot be choosers.
Lucky for you though, I won't use Wikipedia. At any rate, wiki doesn't generally get into this kinda stuff.
The real cause of Indian Nationalism was British Nationalism. Think about it, the British Empire had firm control over the subcontinent and affiliated regions all under the lauded belief that the British were a superior people culturally, religiously, economically and politically. A bit of irony to this was that the efficient British Administration eventually began creating a new social class of well educated Indian administration. This new class wasn't lost to the concept of nationalism that was felt by their British colleagues. Naturally, the Indian leaders who were the vanguard against British rule were the ones who were educated by the British.
there were two important things the British did to this end:
the first, as stated by the previous answer, was to educate some Indians in the Western manner. they learned English (this was the first time the entire subcontinent spoke the same language) and were exposed to Western ideas about self-determination and nationalism, as well as knowledge of previous independence movements in other countries. without ideas of civil disobedience and national solidarity, the Indians could only try to fight their way to independence, which they did in 1857 and were crushed by the British military.
the second, probably more important in both the short and long run, was to unite the Indian subcontinent. aside from the occasional ascendant empire-- Mauryas, Guptas, Mughals, Marathas,-- India was chronically divided. of those empires, only the Mughals were remotely centralized, and none controlled as much territory in India as the British. if nationalism had developed in pre-British India, it wouldn't have been Indian nationalism at all. it would have been Kashmiri nationalism or Panjabi nationalism or Bengali nationalism or Maratha nationalism. you can't have nationalism without a nation.