If a series of three consecutive water samples from one supply all showed the presence of E. coli, what is the most logical interpretation?

The most logical interpretation of three consecutive water samples from a supply all showing the presence of E. coli is that the supply was possibly exposed to human fecal contamination. E. coli is a type of bacteria commonly found in the intestines of humans and animals, and its presence in water indicates the potential for fecal contamination. The consistent detection of E. coli across multiple samples suggests a continuous source of contamination rather than a one-time error or incident.

This finding implies a serious health risk, as E. coli can cause food and waterborne illnesses, and indicates an immediate need for further investigation and possibly remediation of the water supply. Addressing the source of the contamination is crucial to ensure the safety of the water for consumption and other uses.

The other options, while they offer scenarios that could explain contamination in certain instances, do not logically fit the context of consistent E. coli detection across multiple samples. For example, concerns about dirty sample bottles or contamination during handling could explain a single sample showing E. coli but are less plausible when there is a repeated finding across three consecutive samples.