Final answer:
The correct sentence is: Washington wanted to return to Mount Vernon after the Constitutional Convention, but his colleagues persuaded him to become the country's first president.
Step-by-step explanation:
The correct sentence is:
Washington wanted to return to Mount Vernon after the Constitutional Convention, but his colleagues persuaded him to become the country's first president.
The conjunction 'but' is necessary in this sentence to show the contrast between Washington's desire to return to Mount Vernon and his colleagues' persuasion to become the first president. It helps clarify the cause and effect relationship between the two actions.