An object of a preposition is a noun or a pronoun that comes after a preposition such as in, at, of to, by, behind, and on to form a prepositional phrase.
(Indonesian Version)

 

The trip (to the island) (on Saturday) will last (for three hours)

 

This sentence contains three objects of prepositions. Island is the object of the preposition to; Saturday is the object of the preposition on; hours is the object of the preposition for.

 

An object of a preposition can cause confusion in the Structure section of the TOEFL test because it can be mistaken for the subject of a sentence.

Example

To Mike ____ was a big surprise.

(A) really
(B) the party
(C) funny
(D) when

In this example, you should look first for the subject and the verb. You should notice the verb was and should also notice that there is no subject. Do not think that Mike is the subject; Mike is the object of the preposition to, and one noun cannot be both a subject and an object at the same time. Because a subject is needed in this sentence, answer (B), the party, is the best answer. Answers (A), (C), and (D) are not correct because they cannot be subjects.

The following chart outlines the key information that you should remember about objects of prepositions.

 
 

Now, Let’s do and analyze the exercise below:

 
EXERCISE 2: Each of the following sentences contains one or more prepositional phrases. Underline the subjects once and the verbs twice. Circle the prepositional phrases that come before the verb. Then indicate if the sentences are correct (C) or incorrect (I).

1. The name of the baby in the crib is Jack. (C)

     Analysis:

    Subject is The name of baby and Verb is IS. So, it is correct
    The Crib is only object of preposition

2. By the next meeting of the class need to turn in the papers.( I)

    Analysis:

   Verb is need but there is no Subject. So, it is Incorrect
   The next meeting of the class is NOT subject, it is object of preposition

3. The directions to the exercise on page 20 unclear.

    Analysis:

    Subject is The directions but there is no Verb. So, it is incorrect.
    The exercise is not subject, it is object of preposition.

4. Because of the heavy rain throughout the night, the walkways are muddy.

   Analysis:

   Subject is the walkways and Verb is Are. So, it is correct.
   The heavy rain throughout the night is only object of preposition.

5. During the week eat lunch in the school cafeteria.

   Analysis:

   Verb is eat but there is no Subject. So, it is incorrect
   The week is not Subject, it is object of preposition

6. In the morning after the concert was tired.

    Analysis:

   Verb is was but there is no Subject. So, it is incorrect.
   The concert is not Subject, it is object of preposition.

7. In the summer the trip to the mountains is our favorite trip.

    Analysis:

    Subject is the trip and verb is Is. So, it is correct
   
8. In a box on the top shelf of the cabinet in the hallway of the house.

    Analysis:

    No Subject and No verbs.
  
9. With her purse in her hand ran through the door.

    Analysis:

    Verb is ran but there is no Subject. So, it is incorrect.
    Her purse and her hand are only object of preposition

10. At 1:00 in the morning the alarm clock on the table beside the bed rang.

      Analysis:

      Subject is the alarm clock and Verb is rang. So, it is correct

 

Credit : http://www.toeflskill.com