The Southern States wanted to ______ the Union, so the American Civil War ______.
—Do you know the tower ___ in the heart of the city? —Do you mean the one ___ to the north of the city library?
—Do you know ____ the 2011 Xiamen International Marathon was held? —On January 2.
Scientists across the world agree that this is an invention of ____ great significance, ____ invention that will greatly change human life.
---Excuse me, Dad, but I am going to the club to meet my friends in the football team. ---OK.
It is well known to us all that a lot of rivers _______by factories.