What is the title of Queen Elizabeth II's eldest son, Prince Charles?

The title "Prince of Wales" has a long and fascinating history tied to the relationship between England and Wales. Originally, it was a title used by native Welsh rulers. However, in 1301, King Edward I of England, after conquering Wales, bestowed the title upon his own son, Prince Edward, to signify English rule over the region. This was a strategic move to appease the Welsh people by giving them a "native" prince, even though he was English. Since then, it has become a tradition for the heir apparent to the British throne to be granted the title "Prince of Wales." So, while Prince Charles held other titles like Duke of Cornwall, the most significant and well-known title associated with his position as the heir to Queen Elizabeth II was, without a doubt, the Prince of Wales. The other options are incorrect because "The Commonwealth King" is not a specific title, the Duke of Edinburgh was Prince Philip's title, and the King of Ireland hasn't existed since the Act of Union in 1800.