Where would you see footprints that happen due to dirt being left behind inside?
Options:
- roof
- ground
- rug
- surface of earth
- floorboards Let's give stream of consciousness first:

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
Footrpints on rugs can be seen only when foot left behind the dirt on rug. Peple walk on rug usually.
Therefore, the answer is rug.