The subject of the Active Voice is changed into the object of the Passive voice. Also, the object of the Active Voice is changed into the subject of the Passive Voice.
The usage of a "to be" form of verb is necessary while changing the voice of the sentence from Active to Passive.
In Passive Voice, the preposition "by" is used before the object. However, it is optional in some cases.
The Active voice in this question is in Past Indefinite. Thus, the Passive voice will also be in Past Indefinite.
The format of Active voice is: Subject + V2 + Object.
Thus, in Passive voice, the format will be: Object of the active voice (Subjective case) + was/were + V3 + by + Subject of the active voice (Objective case).
For example:
Real Madrid won the Champions League. (Active Voice)
The Champions League was won by Real Madrid. (Passive Voice)
The options except (a) don't follow the correct grammatical format of the Passive Voice.
Therefore, the correct answer is: Superman was created by Marvel Comics.