How do i find the object of the preposition

The object of a preposition is the head noun (or pronoun) within the noun phrase or noun clause.) (In this example, the preposition relates to the noun clause the time we have rushed through life trying to save. The object of the preposition is time, which is the head noun. The word the is modifier!!
Hope this helps:)

D. because a physical change doesn't involve anything that's chemically changing the substance (when you think about physical change, think about stuff like color changes that doesn't change the substances chemical makeup)