--- Talking of travel, have you ever been to Chicago?--- Yes. I _____ it twice while I was working in the US.
Our manager ________ for Shanghai in a few days and he has asked me to find out when the earliest plane ________ next Wednesday.
Stephen Hawking believes that the earth is unlikely to be the only planet _______ life has developed gradually.
The sleeping baby would be scared _______ a sudden loud noise.
--David, are you 1istening to me? ---Sorry, Dad. I _______ to make sense of what the reporter said.
Many approaches have been _______ to control the spread of H7N9 Bird Flu.