HI,
ANSWER IS NOT D!!
THE CURRENT SHOULD FLOW THROUGH THE BULB, IT SHOULD NOT BE SHORTED!
S3 SHOULD ALWAYS BE OPEN! AND EITHER S1 OR S2 SHOULD BE CLOSED (OR BOTH SHOULD BE S1 AND S2 SHOULD BE CLOSED)
SO OPTION B IS THE ANSWER.
ANSWER GIVEN IN THE BOOK IS WRONG!
AND PLZ IF YOU ARE CONFIDENT THEN MOVE ON! DONT WASTE YOUR TIME, THERE ARE ALWAYS MISTAKES IN THE BOOKS.
PLZ APPROVE IF YOU ARE SATISFIED :)