Where would you get a pen if you do not have one?
Options:
- briefcase
- desk drawer
- friend's house
- pocket
- sidewalk
Please answer and provide answer explanation.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
One has to borrow a pen if one does not have it. People tend to borrow stuff from their friends. One goes to a friend's house if one wants to borrow a pen. The final answer: friend's house.