The correct answer is option d - He thinks of King George III as a powerful ruler over a vast dominion.
Emperor Qian Long's opinion of King George III can be inferred as thinking of him as a powerful ruler over a vast dominion.
In the account, it is mentioned that Qianlong demanded that Lord George Macartney, the representative of King George III, demonstrate his respect by kneeling and knocking his head on the ground.
This indicates that Qianlong believed King George III to be a ruler with significant power and authority. Additionally, Qianlong refused Britain's request to establish a permanent embassy in China, implying that he did not view King George III as an equal.