PLEASE HELP!!

water quality tests from a local river show low levels of two heavy metals under the acceptable, legal limit. however, the residents of the town are suffering from numerous stomach ailments and are showing signs of long-term kidney damage. what can scientists infer about the possible reason for the illnesses in the town?

A. heavy metals cause acute effects but not chronic effects.

B. the first metal causes and acute effect compared to the other.

C. the heavy metals have a synergistic relationship when combined.

D. the heavy metals have an antagonistic relationship when combined.