The word "disciplines" in the first sentence of Paragraph 1 means ________.

A．3), the chief concern of the scientists is ________.A. the impoverishment of developing countriesB. the explosion of the human populationC. the reduction of biological diversityD. the effect of global warming

A．Because people can't agree as to what species to protect.
B．Because it is difficult to find an effective way to protect such species.
C．Because it affects the interests of certain groups of people.
D．Because it is a major problem involving a series of legal procedures.