Just found from another forum:
The concern is about the quality of effluents and if it must be conrolled.

A. is out ..talks about "delay".

B. this identifies that the quality of the effluents may infact cause damage, because there is no unanimity on the quality of effluents. This shows tht there is no standard to judge the quality of the effluent and no method to determine if the environment is being damaged or not by a specific effluent. Hence, even if an effluent's quality if controlled, it may still be capable of harming the environment. "whether or not specific environmental damage could be attributed to a particular source of effluent"

C. quantities of effluent ? nothing can be said about that. Moreover, we dont know if the countries are the ones producing the largest quantities of effluents.

D. all of any given pollutant to be controlled and that it reaches North Sea!
Now if the pollutant is controlled then how cant it reach North Sea? Whats the purpose of restrcitive controls? Not sure if i understand.

E. Now why would anyone control/restrict the effluents if the damage can be undone?

What must, of course, be shown, in order to avoid excessively restrictive controls is that?-I am not able to understand the meaning of the sentence.

What are the uniform controls and restrictive controls imply here.........

Can any one explain me the question?

The way I see it is "quality of effluent" is referring to possible concentration of various substances. For example quality of effluent can be bad if it contains a lot of Soldium chloride but that does not mean that it is harmful to environment. Hence to avoid excessive restrictive control it is important to determine whether the source is capable of damaging the environment.