—He ought to have been warned of the danger. —____, but he wouldn’t listen to me.
--You don't look so well, Mary. What's the matter with you? --Why?___________.
China has hundreds of islands, ___________ is Taiwan Island.
You must have waited here for a long time ,___________you?
I don't remember___________ to the airport that year.
A man does not know the difficulty of anything_________ he does it personally.