In passive voice, the object of the active sentence becomes the subject of the passive sentence.
· Active voice: Ishika (subject) saw (verb) the tiger (object) in the forest.
· Passive voice: The tiger (subject) was seen (passive verb form) by Ishika (agent) in the forest.
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)
The correct structure in passive voice is: "The tiger was seen by Ishika in the forest."
Hence, option (c) is the answer.