Answer: He begin to think of ways to improve the lives in his community
Explanation
The answer is "He begin to think of ways to improve the live sin is community because in the text most the the passage identifies the problem, then he thinks about building a generator and the bigger battery.
Why the other answers are wrong
A is wrong because it tells us the solution not the central idea.
C identifies the problem, not the Central idea of the text.
D is wrong because it tells us his decision, it is better than the other answers but not the best.