Option 1: Macartney - Macartney was a British diplomat who served as the Governor of Madras Presidency in the early 19th century. However, he was not instrumental in the introduction of the Ryotwari system.

Option 2: Elphinstone - Elphinstone, also known as Mountstuart Elphinstone, was a British statesman and historian. He served as the Governor of Madras Presidency from 1837 to 1842. However, he was not responsible for the introduction of the Ryotwari system.

Option 3: Thomas Munro - Thomas Munro was a British colonial administrator who played a key role in the introduction of the Ryotwari system in the Madras Presidency. He implemented this system in the early 19th century, which aimed to make individual farmers (ryots) the direct owners of land and collect revenue directly from them.

Option 4: John Lawrence - John Lawrence was a British colonial administrator who served in various positions in India. However, he was not involved in the introduction of the Ryotwari system in the Madras Presidency.

Therefore, the correct answer is option 3, Thomas Munro, who was instrumental in the introduction of the Ryot