|Question 8Verbal

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Scientists study the abundance and the activity ratios (AR)-the relative radioactive decay rates of two isotopes-of uranium (U) isotopes in bodies of water to track sediment transport and deposition and to monitor groundwater quality. However, isotope abundance and AR are not always uniform across a single body of water, which may affect the reliability of results if sampling is not sufficiently representative. Chen Zhao et al. analyzed concentrations of the isotope U-238 and the AR at multiple depths and locations in two lakes in China, finding no significant variation in values within the same lake.
Information in the text best supports which statement about Zhao et al.'s findings?
They illustrate why scientists investigating sediment transport and deposition and groundwater quality ought to evaluate how evenly U abundance and AR are distributed in the bodies of water they are examining.
A
They challenge the assumption that U abundance and AR sometimes vary from lake to lake, since the U-238 concentration and U-234/U-238 AR were consistent across the sampled lakes.
B
They indicate that researchers performing isotopic analysis in the lakes Zhao et al. studied can likely rely on localized sampling within each lake, since values from any one location or depth are representative of the entire lake.
C
They demonstrate that the number of samples Zhao et al. collected from the two lakes is sufficient to yield equally reliable information about sediment transport and deposition and groundwater quality in those two lakes.
D