Correct Answer: It is known to me that his guitar will be played by him.

Solution : The correct choice is the third option.

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 given sentence has two parts. The first part, "I know", is in the simple present tense.

• So, the structure of the passive voice in the case of the simple present tense is: "Singular object + is + past participle form of the main verb + prepositional phrase."

And the second part of the sentence, "he will play his guitar", is in the simple future tense.

• So, the structure of the passive voice in the case of the simple future tense is: "Singular object + will + be + past participle of the main verb + by followed by the agent of the action."

Therefore, the correct answer is: "It is known to me that his guitar will be played by him."