The correct answer is option 1: Lord Curzon.

The Indian Agriculture Service (IAS) is a specialized civil service in India that deals with agricultural administration and rural development. It was established to address the needs of the agricultural sector and improve agricultural practices in the country.

Lord Curzon, who served as the Viceroy of India from 1899 to 1905, played a significant role in the establishment of the Indian Agriculture Service. He recognized the importance of agriculture in India`s economy and sought to improve agricultural productivity and modernize agricultural practices.

While the other options mentioned in the question were also influential figures in Indian history, they were not directly responsible for starting the Indian Agriculture Service. William Bentinck served as the Governor-General of India from 1828 to 1835 and focused more on social and administrative reforms. Lord Minto served as the Viceroy of India from 1905 to 1910 and focused on political reforms and defense matters. Lord Ripon served as the Viceroy of India from 1880 to 1884 and focused on educational and constitutional reforms.

Therefore, Lord Curzon is the correct answer for starting the Indian Agriculture Service.