Correct Answer: The letter was lost by the manager.

Solution : The second option is correct.

In the original sentence, the structure is in active voice. The passive voice is the voice in which the object experiences an action rather than the person who performs the action. Hence, the object in the active sentence becomes the subject in the passive voice.

• The structure of a passive sentence in case of the simple past tense is, Singular subject + was + past participle form of the main verb + by followed by the agent of the action.

Therefore, the correct answer will be: " The letter was lost by the manager."