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 environmental damage could be attributed to a particular source of effluent. What must, of course, be shown, in order to avoid excessively restrictive controls, is that __ . Which of the following best completes the passage below? ['any uniform controls that are adopted are likely to be implemented without delay', 'all of any given pollutant that is to be controlled actually reaches the North Sea at present', 'any substance to be made subject to controls can actually cause environmental damage', 'the countries favoring uniform controls are those generating the largest quantities of effluents']