U.S. President Barack Obama arrived in China’s economic center Shanghai on Sunday night, November 15th 2009, ______a state visit to China.
It was ten o’clock _____ he came back home.
“Where _______ go to work?” “Where _______ go to work is not known.”
It was when she was about to go to bed ______ the telephone rang.
None knows if _______ that boy, but if _______ him, her parents will be disappointed.
The problem is _____ has caused us a lot of trouble.