Can you give me some examples of a objective of the preposition in a sentence?

What you want is the "object" (not objective) of a preposition. In grammar, a preposition is a Word that shows location (on, in, up, down, into, at, to, with, inside, outside, under, over... just to name a few). A prepositional phrase is a group of Words made up of a preposition along with an article (a, an, the) and a noun. For example: "in the kitchen"; "at the movie"; "in a classroom." Sometimes, you don't need any article: In Boston. At school. So, the object of a preposition refers to that noun in the prepositional phrase. Note: the noun which is the object of a preposition can never be the subject of a sentence. It can only be used in the prepositional phrase.

Some examples of the object of a preposition: We were swimming in the ocean. (The preposition is "in," the object in "ocean.") Dana walked her sister to the bus. ("To" is the preposition, and the object is "bus.") Bob and Maria went to the movie with their friends. (This one has two prepositional phrases: "to the movie" and "with their friends." The objects are movie, and friends.)