Answer : 2. "Ancient water supply system"
Explanation :

Recently in response to severe water shortages in dry areas of Africa, the ancient “qanat system” has been proposed as a solution. Originating in arid regions around the world, this water-supply system channels mountain water through sloped tunnels to address limited water supply. It is known by various names in the regions, such as “fogara ” and “Falaj”, qanat have been used for centuries in regions such as North Africa, the Middle East and Asia. This gravity-based system, which does not require electricity, provides sustainability, minimal evaporation and extensive irrigation potential, thereby promoting social cohesion.