Select the option that expresses the given sentence in passive voice.
I have not discouraged him from doing anything.

Correct option is C

"He has not been discouraged from doing anything by me." is the correct passive voice transformation, maintaining the present perfect tense.
Conversion rule: Subject + has, have + not + V3 + object -> <- Object + auxiliary verb (has, have) + not + been + past participle + by + subject.