The correct option is D Is solving social problems
Option D is the most appropriate answer for this question because Surti is working towards water conservation. Water wastage is a serious threat to the city and so is water scarcity. By repairing the pipes and taps, Surti is doing his best to avoid wastage of water which is often a neglected issue. He is working on a grass-root level and by rendering his services for free to everyone, he is indeed solving the social problems.