Option 1, W.C. Banneiji, is not the correct answer. While Banneiji was an important figure in the Indian national movement, he did not propound the theory of the `Economic Drain of India` during British imperialism.

Option 3, Gopalkrishna Gokhale, is also not the correct answer. Gokhale was a prominent social and political leader, but he did not specifically put forward the theory of `Economic Drain of India`.

Option 4, Gandhiji, is not the correct answer either. While Gandhiji played a crucial role in the freedom struggle, he did not come up with the theory of `Economic Drain of India`.

The correct answer is option 2, Dadabhai Naoroji. He is known for propounding the theory of `Economic Drain of India` during British imperialism. Naoroji highlighted how India`s wealth was being drained by Britain through economic policies like the imposition of heavy taxes and the export of raw materials. He advocated for economic reforms to address this exploitation.