They are both in motion because an object is not at rest, but moving so slow it could be at rest. A car going at the same constant velocity is neither speeding up or slowing down, an object "at rest" is also moving at a constant rate, not speeding up or slowing done.
The SI unit of time is second
The answer is D interferometry
the answer is A.
because it says THE AIR which means there is air in the balloon
