The correct answer for the question asked is Option B.
The passage talks about the National award winning author, Abid Surti and his efforts towards ensuring one of the major problems that Mumbai, as well as the world in a macro aspect is facing right now: Water wastage. The reason, why he does this and how far reaching his efforts are, forms the crux of the passage.
Option B, speaks of checking water wastage, which is clear from his efforts of going from door to door, to check whether there are any cases of loose pipes. This is an initiative towards ensuring less water wastage.
The other options A, C and D are not in accordance with what Mr. Surti actually aims to do, but are only branches of what his mission actually is, hence eliminating them as answers.