The beautiful song ________ me of those happy old days we had spent together.
21. The third and last chapter _______ by Professor Chen.
22. --- No, I’m afraid he isn’t in. This is his secretary speaking. Can I help you? --- _______.
23. _______ the plane have taken off on time? --- I’m afraid not. The fog was too thick then.
24. The car ran into a crowd of middle school students, _______ to hospital immediately.
25. The sooner one _____ to the new working conditions, the better it will be _______ his working efficiency.