Daniel paused to examine a leaf on the sidewalk. These falling leaves mean only one thing: the last days of summer were drawing
to a close. Soon his sister Natalie would leave for college. He realized that time was short, and he needed to keep his promise to get her the best graduation present ever. When is this passage set? Which verb in the passage sets the overall tense? Which verb or verb phrase has an inappropriate shift in tense? Which verb or verb phrase would you use to correct the inappropriate shift in tense?
Prepositions must always be followed by a noun or pronoun. That noun is called the object of the preposition. Note that a verb can't be the object of a preposition.