Which example represents passive voice correctly?

The passive voice is characterized by the subject of the sentence being acted upon rather than performing the action. In this instance, the sentence "The book was given to Sarah by Harry" illustrates this perfectly. Here, "the book" is the subject receiving the action of being given, while "Harry" is the doer of the action who appears later in the sentence, introduced by the preposition "by."

This structure emphasizes the recipient of the action (Sarah) and the action itself (being given) rather than focusing on the doer. Utilizing passive voice can be particularly useful in writing when the emphasis should be on the action or the recipient rather than who performed it.

The other examples provided are all in active voice, where the subject actively performs the action. This distinction makes the passive voice in the highlighted example stand out as correct.