Everyone knows that _____ is dangerous to play with fire, but _____ is difficult is to prevent children from playing with fire.
I called the airline to________my flight reservation a week before I left for Toronto.
__________ has been announced, we shall have our final exam next month.
You are saying that everyone should be equal, and this is ______ I disagree with you.
The lazy waiter ______ to his boss that he had ______ the table.
We all know the truth _____ there are air, water and sunlight there are living things.