Explain why an action such as cleaning up the garbage in a park is not a sustainable action on its own. What else is needed along with such an action to make it sustainable?

Will give brainliest asaapppppppppppp plz im in a major hurry to finish which of these pairs of objects exerts the greatest gravitational force on each other? object 1 and object 3 object 4 and object 3 object 1 and object 4 object 4 and object 2