GMAT Critical Reasoning (CR) | Re: At a recent conference on environmental threats to the North

So there are 100 items. The quality of 50 effluents restricted to lets say 20% concentration. Now what does 'excessive restriction' mean? quality reduced to 10% concentration of those 50 effluents OR restriction now applied to 80 (instead of 50) effluents?

Please advise on how to decide where the restriction means the restriction on quality or restriction on number of effluents?

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