Correct Response: D. The scientist's conclusion would be undermined if the uncontaminated test wells were found to be drawing water from a different aquifer than the contaminated confined aquifer that supplies the drinking-water well. The test wells that are up-gradient from the drinking water well (A) would flow down-gradient to the drinking water well so that does not affect the validity of the scientist's conclusion. The fact that the pump at the contaminated test well was off when samples were collected (B) does not undermine the scientist's conclusion as contaminant levels would be higher if anything in a pumping well. There are strict protocols for collecting water samples that professional scientists are required to follow and the samples are processed in a laboratory, so having more than one person collect the samples (C) does not reduce the validity of the scientist's conclusion either.
