He ____ writing the paper now. He hadn’t written a single word when I left him ten minutes ago.
This machine _______. It hasn’t worked for years.
I would rather _____ a little earlier to avoid ________in the rush hour traffic.
He speaks English well indeed, but of course not ______ a native speaker.
It was ____ that he had to ask for help.
Pierre Curie stopped his research and _______ Marie in the search of an unknown material.