Which of the Following Is False About Research on the Effect

Which of the following is false about research on the effect of environmental toxicants on human health?

A) Most knowledge about specific impacts of toxic exposures is based on experiments using nonhuman animals.
B) It is not easy to determine exactly how, and to what extent, environmental toxicants affect human health.
C) Research done with humans is typically experimental rather than correlational.
D) Cumulative or interactive effects of toxicants will typically go undetected by researchers.