I think it is D
Hope my answer help you?
Answer:
<h2>C. maintenance </h2>
Explanation:
I personally believe one key disadvantages is the cost of maintaining the equipment unlike the gym where you have to subscribe for the month or the year and forget about anything, owning the gym equipment comes with the extra cost and responsibilities of maintenance to the owners.
I believe it’s (D. Any object)
A. Made of the marble.
the mass remains constant when you drop the marble but the rest of the variables change as the marble is dropped, therefore, the only constant variable is its mass.