If receiving water is to be used as the dilution water, caution must be exercised in exposing the test organisms to it, because of the possibility that it might be toxic.
Water always has possibility of being toxic.
mnli hypothesis: Water always has possibility of being toxic. premise: If receiving water is to be used as the dilution water, caution must be exercised in exposing the test organisms to it, because of the possibility that it might be toxic.