Explanation

• The correct answer is: Grass is not eaten by a lion, however hungry he may be.
• This sentence is in the passive voice, whereas the original sentence "Lion does not eat grass, however hungry he may be"
• is in the active voice.
• In the passive voice, the focus is on the grass (the object) rather than the lion (the subject),
• and the verb phrase "is not eaten" is in the passive form.