From the passage we know that Negroes _______.

A．Legislation and government intervention.
B．The industry's understanding and support.
C．The efforts of environmental health professionals.
D．The cooperation of ecologists, environmental activists and conservationists.

A．Inevitable phenomenon of social developing.
B．Few people are aware of it.
C．The tax exerted on manufacturer is too heavy.
D．Difficulty in affixing legal responsibility on the people who caused the problem.

A．They were ignored.
B．They were condemned.
C．They were belittled.
D．They were praised.