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
Analysis :
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.
OBJECT OF PREPOSITIONS
A preposition is followed by a noun or pronoun that is called an object of the preposition. If a word is an object of a preposition, it is not the subject.