Final answer:
The correct answer is 'resign'. Without a hyphen, it means to quit, but with a hyphen ('re-sign'), it means to sign a contract once more, often used in pro sports.
Step-by-step explanation:
The student is asking about a word's meaning and how adding a hyphen changes that meaning. Specifically, they are looking for a 6-letter word that means "to quit" which, when a hyphen is added, can mean "to join again," especially in a professional sports context. The correct answer is resign. Without a hyphen, 'resign' means to quit. However, when a hyphen is added, the word becomes 're-sign,' meaning to sign a contract again, often used when a player signs a new contract with the same professional sports team.