$\text{The performance had hardly begun when the lights went out.}$
$\text{⇒ Answer: Scarcely had the performance begun when the}$
$\text{lights wents out.}$
$\text{Tạm dịch: Buổi diễn khó được bắt đầu khi đèn bị tắt.}$
$\text{Cấu trúc đảo ngữ: Scarcely + had + S + PII when S + V-ed/irregular.}$