_______ is known to us all that the old scientist, for _______ life was hard in the past, still works hard in his eighties.
The work he paid special attention _____ to nothing.
The life he is now used _____ quite different from ours.
The old house we paid a visit _____ at the top of the hill.
Nothing that he suggested _____ to be of any use.
What the boy enjoys _____ to have a room of his own.