Answer:
D. Kelly and Avery walk the same distance.
Explanation:
Kelly walked from the 1st floor to the 5th floor. That means she walked 4 floors. 
Avery walked from the 8th floor to the 4th floor. 
8 - 4 = 4. 
They walked the same distance, except Avery went down, and Kelly went up, which is unrelated.