The correct answer is: Rivers.
Rivers are the major source of irrigation in Manipur. The state has a number of rivers, including the Imphal River, the Thoubal River, and the Barak River. These rivers are used to irrigate crops, such as rice, sugarcane, and vegetables.
Canals are also used for irrigation in Manipur. However, they are not as important as rivers. The state has a number of canals, but they are not as well-developed as the canals in other parts of India.
Tanks are not a major source of irrigation in Manipur. The state has a few tanks, but they are not as important as rivers or canals.
Groundwater is also not a major source of irrigation in Manipur. The state has a limited amount of groundwater, and it is not as easily accessible as groundwater in other parts of India.
In conclusion, rivers are the major source of irrigation in Manipur. The state has a number of rivers, which are used to irrigate crops, such as rice, sugarcane, and vegetables. Canals are also used for irrigation in Manipur, but they are not as important as rivers. Tanks and groundwater are not major sources of irrigation in Manipur.