There are __________ flowers in the square during National Day.

Have you returned the book to the library _______?––Yes, I have _________ returned it.

Have you mended your shoes, Bob？—Yes, I _________ them twenty minutes ago ．

Mr. Wang is a teacher. He ______ in this school for 20 years.

The English-Chinese dictionary ____my father bought for me many years ago is so useful.