Usually a child's behavior is a ________ of his family environment.
She ________a chain to the dog's collar.
You can take as many as you like, because they are free of________.
—Who is the man ________here? —Captain Cook.
—Are the new machine working? —Yes. Three million tons of coal________exploited every year in the city.
Everyone here thanks the firefighters for the things they have done to prevent fires________the environment safer.