Tankas are _______

Option 1 -> Describes underground rainwater harvesting storage tanks, cemented to store rainwater for drinking.

Option 2 -> Refers to glacier-fed water collection systems, not tankas.

Option 3 -> Describes canal irrigation systems for water distribution.

Option 4 -> Refers to irrigation channels for agricultural water supply.

Hence, Option 1 -> Tankas are traditional underground water storage structures, commonly found in Rajasthan and other arid regions of India, where they are cemented or plastered to collect and store rainwater, particularly for drinking purposes during dry seasons -> correct