Explanation:

- Original sentence: "I know him." This is in active voice, where the subject "I" performs the action of knowing on the object "him."

- Option 1: "I am known to him."

- This suggests that the subject "I" is the one who is known, not the one knowing. It's not a correct passive transformation of the original sentence.

- Option 2: "He is known to me."

- This is the correct passive voice version of the original sentence. The original object "him" becomes the subject "He," and "to me" indicates who knows him.

- Option 3: "Let him be known to me."

- This reads as a suggestion or command rather than a passive transformation. It changes the meaning of the original sentence.

- Option 4: "He is known to myself."

- This is grammatically incorrect because "myself" is reflexive and should not be used here.