It is immediately obvious that water is to be _______ to the development of life.
If we________ , we can realize the progress we have made in space research.
They arrived at the farmhouse, in front of which _________.
—Who are those with the flags? —A group________itself the League for Peace.
When I was you age, I dared to go out alone at night, ________ you?
Everything he ______ away from him before he returned to his home town.