The document discusses the passive voice in grammar. It explains that in the passive voice, the object of the active sentence becomes the subject of the passive sentence. It also notes that the original subject becomes an agent following the preposition "by". Only transitive verbs can be used in the passive voice. The format for the passive voice is to use some form of "to be" plus the past participle of the main verb. The passive voice is used when the performer of the action is unknown, unimportant, or to later specify the performer by adding "by" and the agent. Both direct and indirect objects can become the subject in a passive sentence. When changing an active sentence to the passive, the tense and agreement between the