Car is moving on the glassy slope with constant speed
Now we know that

so acceleration is rate of change in velocity
as we know that velocity is constant here so acceleration is zero
so here

now as we know by Newton's II law

since a = 0

so net force will be ZERO on it during this motion
B. The velocity of the second flight is negative compared to the speed.
Your answer will be Radio Waves .
That seems to be the only to make sense. Hope that helps u