Select the option that expresses the given sentence in passive voice.

I know him.

He is known to me.

The correct passive form of the given sentence is He is known to me.

The active voice of the sentence is I know him. This sentence is in the simple present tense, which is used to describe an action that happens regularly. The passive voice of the sentence is formed by putting the subject of the active sentence after the verb "to be" and the past participle of the main verb. In this case, the subject of the active sentence is "I" and the main verb is "know." The past participle of "know" is "known." So, the passive form of the sentence is He is known to me.

The other options are incorrect because:

• I am known to him. is also in the passive voice, but the subject of the sentence is "I."
• He is known to myself. is grammatically incorrect. The pronoun "myself" should not be used as the object of a verb.
• Let him be known to me. is in the imperative mood, which is used to give commands or make requests.