I had wanted to visit the gallery before I            Florence, but it' s closed on Sundays.

---Has Tom finished his composition yet?　 ---I have no idea, he _____ it this morning.

This book is said to be a special one, which __________many events not found in other history books.

He looked as though he _________ a ghost（鬼）.

—Why do you look so puzzled?—Oh，I ________ over a most difficult maths problem.