The correct option is B Lord Cornwallis
Amar singh was the youngest son of Pratap Singh. He became the regent after the death of Thuljaji and ruled Thanjavur in the name of Thuljaji's adopted son Serfoji II. Later he claimed the throne as Serfoji was the adopted son. Due to the support of Britishers, he became the ruler but he ruled arbitrarily so Lord Cornwallis removed him and made Serfoji II as a king.