The Dose-Response Curve for Arsenic

The dose-response curve for arsenic

A) Shows no benefit to low concentrations and great harm from high concentrations.
B) Shows that arsenic is beneficial to humans when consumed in low quantities, but toxic at high quantities.
C) Was a major factor in setting the new, lower drinking-water standard for dissolved arsenic of 10 ppb in public water supplies.
D) Shows that microorganisms can be very helpful in decontaminating a site with high arsenic levels.