Creating better health care, education and housing for everyone is a simple idea, but ____ which is hard to put into practice.
--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.