The correct answer is: Surface irrigation.
Surface irrigation is the most common method of irrigation in Assam. It is a method of irrigation in which water is applied to the surface of the soil, either by flooding or by spraying. Surface irrigation is a simple and inexpensive method of irrigation, but it can be inefficient, as much of the water can be lost to evaporation or runoff.
Flood irrigation is a type of surface irrigation in which water is applied to the soil surface in a sheet. This method is often used in areas with flat terrain, as it requires little infrastructure. However, flood irrigation can be inefficient, as much of the water can be lost to evaporation or runoff.
Sprinkler irrigation is a type of surface irrigation in which water is sprayed onto the soil surface from above. This method is often used in areas with uneven terrain, as it can be used to irrigate areas that are not accessible by flood irrigation. However, sprinkler irrigation can be more expensive than flood irrigation, as it requires more infrastructure.
Drip irrigation is a type of irrigation in which water is applied directly to the roots of plants. This method is often used in areas with limited water resources, as it is very efficient. However, drip irrigation can be more expensive than other methods of irrigation, as it requires more infrastructure.
In Assam, surface irrigation is the most common method of irrigation because it is a simple and inexpensive method that can be used in a variety of terrain. However, surface irrigation can be inefficient, as much of the water can be lost to evaporation or runoff.