The Ryotwari experiment in land revenue was started by Alexander Reed. The Ryotwari system was a method of collecting land revenue introduced by the British during their rule in India. Under this system, individual farmers, known as ryots, were given direct control over their land and were required to pay the land revenue directly to the government.

Option 1, Henry Dundas, is not the correct answer. Henry Dundas was a Scottish politician and lawyer who served as the President of the Board of Control for India. Although he had some influence over British policies in India, he was not directly involved in implementing the Ryotwari system.

Option 3, David Ricardo, is not the correct answer either. David Ricardo was an economist who developed the theory of comparative advantage and made significant contributions to the field of economics. He was not involved in the implementation of land revenue systems in India.

Option 4, Mountstuart Elphinstone, is also not the correct answer. Mountstuart Elphinstone was a Scottish statesman and historian who served as the Governor of Bombay during the British rule in India. While he made significant contributions to the administration of India, he was not specifically responsible for starting the Ryotwari experiment.

Overall,