Helppp ạ.

`50` Only later did I realize who he was .

`-` Đảo ngữ ''only after'' : Only after + trợ động từ + S + V + O ...

`51`  Only when all the guests had gone home could we relax .

`-` Đảo ngữ ''only when'' : Only when + S + V + O + trợ động từ + S + V + O ...

`52` Had it not been for the deadth of the Prime Minister , the passing of the bill wouldn't have been prevented .

`-` Đảo ngữ điều kiện loại `3` : Had + S + V3/V_ed + O , S + would/could + have + V3/V_ed + O ...

`53` Not until he received the offer of promotion in writing did John celebrate .

`-` Đảo ngữ ''not until'' : Not until + S + V(quá khứ) + O + trợ động từ + S + V .

`54` Only by training hard every day can you become a good athlete .

`-` Đảo ngữ ''only by'' : Only by + trợ động từ + S + V + O ...

`55` Only after the flight left had they to wait for twelve hours .

`-` Đảo ngữ ''only after'' : Only after + trợ động từ + S + V + O ...

`56` At no time was the result of the match in doubt .

`-` Đảo ngữ ''at no time'' : At the time + trợ động từ + S + V + O ...

`57` Never have there been more people out of work in this country .

`-` Đảo ngữ ''never'' : Never + have/has + S + V3/V_ed + O ...

`58` Not until I left home did I realize how much my father meant to me .

`-` Đảo ngữ ''not until'' : Not until + S + V + O + trợ động từ + S + V + O ...

`60` At no time did he suspect that the money had been stolen .

`-` Đảo ngữ ''at no time'' : At the time + trợ động từ + S + V + O ...

`61`  Had it not been for the attendance of a famous film star, the party wouldn't have been a success .

`-` Đảo ngữ điều kiện loại `3` : Had + S + V3/V_ed + O , S + would/could + have + V3/V_ed + O ...

`61` Never in my life have I seen such a mess .

`-` Đảo ngữ ''never'' : Never + have/has + S + V3/V_ed ...