Which of the following is a requirement for an EPA-registered disinfectant?

An EPA-registered disinfectant must meet certain efficacy standards to ensure it effectively kills pathogens. One common chemical used in disinfectants is chlorine, and having a minimum strength of 100 parts per million (ppm) of free available chlorine is considered a standard for effective disinfection against a range of microbes. This concentration is necessary to ensure that the disinfectant is potent enough to eliminate bacteria, viruses, and fungi effectively.

The other options do not accurately represent requirements for EPA-registered disinfectants. For example, while color and fragrance might be added for marketing purposes, they are not foundational requirements for the product's disinfecting capability. Safety for ingestion is also not relevant, as disinfectants are not intended for consumption. Additionally, while testing for efficacy is important for ensuring that a disinfectant works, it does not specify a daily testing requirement as a condition for the product's registration with the EPA. Thus, the focus on the specific concentration of chlorine as a requirement for effectiveness is what makes this option correct.