The correct answers are: Not only did the chef drop the wedding cake, but he also accidentally stepped on it. Never before had I seen a chocolate soufflé deflate with such a sad little sigh. Little did the judges know that the secret ingredient was actually catnip.

When a negative or limiting adverb (like not only, never, or little) is placed at the beginning of a sentence for dramatic emphasis, it triggers subject-auxiliary inversion. The auxiliary verb (did, had) must come before the subject.

Incorrect Options:

• Under no circumstances you should... is incorrect because it lacks inversion. It should be: "Under no circumstances should you eat..."

• No sooner the timer rang... is incorrect because it lacks an auxiliary verb. It should be: "No sooner had the timer rung..." or "No sooner did the timer ring..."