The correct option is B Subsidiary Alliance
The doctrine of subsidiary alliance was introduced by Lord Wellesley, British Governor-General in India from 1798 to 1805. As per the system, Indian rulers were not allowed to have their independent armed force. They were to be protected by the company, but had to pay for the 'subsidiary forces' that the company was supposed to maintain for the purpose of this protection. It played an important role in the conquest of lndia.