The correct answer is option 1, Ganga. The Ganga river serves the largest cultivable area in India. The Ganga river, also known as the Ganges, is one of the major rivers in India and is considered sacred by Hindus. It flows through several states, including Uttarakhand, Uttar Pradesh, Bihar, and West Bengal, before emptying into the Bay of Bengal. The fertile plains along the banks of the Ganga, known as the Gangetic plain, are highly suitable for agriculture and support a large cultivable area. The river provides water for irrigation, enabling farmers to grow crops and sustain their livelihoods. Its extensive coverage and significance make it the river that serves the largest cultivable area in the country.