She was so tired from the flight that she went straight to bed, leaving all the luggage _____.

Now mobile phones are not so expensive as they _______ to be.

I tried to find ________ that prevented so many people from taking part in the program

I think students may bring iPad to school.–_________ This can cause some trouble.

ent Obama held talks with ChinesePresident Hu Jintao in Beijing, ________ economic recovery, climate change andstopping the spread of nuclear weapons