In the past few years, so many areas throughout the world have been hit by such destructive earthquakes, snowstorms and tsunamis ________ we have never experienced before, ________ makes us worried a lot about nature disasters

Finally, Susan got married ____ a businessman.

It is the first time that I ______________ such a beautiful scene

The book was written ______ careful observations and detailed studies

You’d better call the airline to ____ your flight reservation a week before you leave for Ottawa. [ ]