Are you willing to live on Mars one day –_____ It sounds exciting， but it still worries me.

Some pictures of the river brought the days back to the oldthey swam in it .

May I speak to your manager MrWilliams at five o’clock tonight?–I’m sorryMrWilliams _______ to a conference long before then.”

I visited the Qinhu Lake last Sunday. —______ Why didn’t you tell me earlier?

Qian Xuesen passed away on Octorber 31, 2009 the age of 98, but he is a manstill encourages Chinese youth.