Option 1: Warren Hastings - Warren Hastings was the first Governor-General of Bengal. He served from 1772 to 1785. During his time, Tipu Sultan was not a major threat, and there is no evidence to suggest that he formed a Triple Alliance against him. Therefore, this option is not correct.
Option 2: Lord Cornwallis - Lord Cornwallis was the Governor-General of Bengal from 1786 to 1793. He is known for his policies towards Tipu Sultan. In 1792, Cornwallis made a treaty with Tipu Sultan, known as the Treaty of Seringapatam. This treaty brought temporary peace between the British East India Company and Tipu Sultan. So, it is correct to say that Lord Cornwallis formed the Triple Alliance against Tipu Sultan.
Option 3: Lord Wellesley - Lord Wellesley was the Governor-General of Bengal from 1798 to 1805. He was responsible for planning and executing the Fourth Anglo-Mysore War against Tipu Sultan. However, the question asks about the Governor General who formed the Triple Alliance against Tipu Sultan. Lord Wellesley did not form a Triple Alliance against Tipu Sultan, but rather led the British forces against him individually. Therefore,