_____ is known to us all is _____ the theme of Shanghai Expo is “Better city, better life”.

— I wonder ________ you’ll water this kind of flower. —Once a week. 

If you sleep less than 7 hours a day, you are more     to catch a cold.

______ Marx's works with Engels', and you'll find many differences．

Having been born on the earth, we had no choice but ________ hospitality it offered.