The phrase ‘set off’ is a commonly used English phrasal verb that means to leave a place, especially to begin a journey or to start moving toward a destination.
For example:
• We set off early in the morning to reach the mountains by noon.
• They set off for the airport as soon as it started raining.
The phrase can also have other meanings depending on the context, such as:
• To cause something to start or trigger an action (e.g., "The loud noise set off the alarm").
• To highlight or enhance something (e.g., "Her red dress set off her fair complexion").
However, in the given question, the meaning that fits best is “to leave a place”—that is, to begin a journey or to start traveling.
Final Answer: to leave a place