For how many families, total savings is negative over the given period?
This question set is purely based upon observation. That also, very careful observation.
Sharma, Sinha and Patel family have negative total savings. Hence option (b) is the answer. Following is the detailed list of savings:
20062007200820092010SummationVerma200−100100100100400Sharma100−100−200−100100−200
20062007200820092010SummationSinha−100−100−300−100400−200Patel−100−100100−200−200−500Agrawal1001000100200500