Hello this is to other people looking for the answer. Everyone else is wrong. I just took the quiz on e2020. The answer actually Comparative. Your welcome. Have a nice day.
Answer:

Explanation:
The density changes means that the length in the direction of the motion is changed.
Therefore,

Given :
Side, b = h = 0.13 m
Mass, m = 3.3 kg
Density = 8100 
So,


l = 0.024 m
Then for relativistic length contraction,







Therefore, the speed of the observer relative to the cube is 0.9833 c (in the units of c).
The answer is "heat transfer."
Average speed = total distance / total time.
That's 172 km / 5 hr = 34.4 km//hr