Where would you keep a business telephone directory?
Options:
- office
- house
- book shelves
- phone booth
- building
Let's think carefully first. Step-by-step reasoning process:

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
Business telephone directory contains business contacts. Business contacts are kept in office for their easy retrieval. So the final answer is office.