Hercules C1 Grammar Quest

Which sentence correctly uses inversion after a negative adverbial?

• Seldom Hercules faced such a challenging foe as the Hydra.
• Hardly Hercules has recognized his true potential when Zeus called him home.
• Never had Hercules encountered a monster more ferocious than the Hydra.
• Under no circumstances Hercules should give up on his quest.

Explanation

After a negative adverbial (e.g., never, seldom, rarely), invert the auxiliary and subject (had Hercules encountered).