题目选项分析

Researchers in City X recently discovered low levels of several pharmaceutical drugs in public drinking water supplies. However, the researchers argued that the drugs in the water were not a significant public health hazard. They pointed out that the drug levels were so low that they could only be detected with the most recent technology, which suggested that the drugs may have already been present in the drinking water for decades, even though they have never had any discernible health effects.

Which of the following, if true, would most strengthen the researchers' reasoning?

【选项】Even if a substance in drinking water is a public health hazard, scientists may not have discerned which adverse health effects, if any, it has caused.