That would be the atom I believe.
The 1st one goes two added sodoes the second one then the third goes to removed then the fourth goes to added and the rest go to removed
Answer:
In terms of distance, average speed is 20 km/h
In terms of displacement, average speed is 0 km/h.
Explanation:
Total distance:

Total time is 3.0 hours
but:

In terms of distance.
substitute:


In terms of displacement:

OMG ITS B ITS B I HOPE I HELPED U
I believe it is D. Earth spinning on it's axis.