Mountain climbing _______ be tiring and many people feel sick as the atmosphere gets thinner.

 Mr. Li, a man calling himself Smith wants to see you. ________ he come in?

No wonder you caught a cold. You________have gone out last night without a coat.

Jack is a great talker.   It’s high time that he              something instead of just talking.

I ________ more information I needed, but my computer broke down.