The concept of the of distance is illustrated by the fact that as cost increases with distance, interactions between people decrease.
a. friction
b. flexibility
c. relativity
d. erosion

I believe it is relativity. I think this because erosion is a scientific term to describe the process of an area of earth dissolving, or eroding away, from weather or the ocean. Flexibility is being able to have a body that is very flexible, while friction is another term used to describe the force accumulated from two objects touching. So, the most likely answer is relativity.

Well the magnitude of its acceleration related to that car starts with the oil change like when you have to change the oil in your car you have to make sure that your precious car is starting really propley and very well