Answer: Hello there!
if you want to know the distance between two points, you need to calculate the difference between them.
if the basement floor is at -14 ft, and the roof is at 36 ft, then the distance between the basement floor and the roof is: 36 ft - (-14)ft = 36ft + 14ft = 50 ft
You can see that we obtained a positive number, this is because we define positive to the upward direction, so if you are in the basement, you need to do 50 ft upwards to reach the roof.
then the correct answer is D.