I believe it is b electric energy etc...
Since f=ma assuming you knew the mass of the marble and the total amount of force acting on it than you would divide the amount of force by the mass.
I feel like it is important, because it is always nice to learn about new things and keep your mind open, to expand your knowledge.
<span>1 Cu + 2 H</span>₂<span>SO</span>₄<span> = 1 CuSO</span>₄<span> + 2 H</span>₂<span>O + 1 SO</span>₂
Coefficient od CuSO₄ = 1
hope this helps!