At a recent conference on environmental threats to the North Sea, most participating countries favored uniform controls on the quality of effluents, whether or not specific environment damage could be attributed to a particular source of effuent, what must, of course be shown , in order to avoid excessively restrictive controls, is that____
A)..
B) any substance to be made subject to controls can actually cause envornmental damage
C)..
D) all of any given pollutant that is to be controlled actually reaches the North Sea at present
I would like to know how can we exlude D, I think both B and D are right. | 
