Wuhan , once called Chicago of East by Mr. Sun Yatsen , has become a prosperous city in central Hubei .
Someone is at the door. ________ must be Mr Smith.
Mr Smith is at the door. _______ wants to see you.
I’ve no idea. I just pretended nobody was at home, so I didn’t ask who _______ was.
I dislike _______ when others laugh at me in public or think poorly of me behind.
Everyone knows that _______ is dangerous to play with fire, but _______ is difficult is to prevent children from playing with fire.