resh air, ________

Many scientists believe that the universe began with an enormous explosion called the “Big Bang”, ______ happened about 13.7 billion years ago.

Can your sister play tennis– Sure. She plays ____ I do.

____, are you Ben—No, I’m not. I’m Peter.

My pain _______ apparent the moment I walked into the room, for the first man I met asked sympathetically， “Are you feeling all right?”