Final answer:
Chlorine reacts with water to form hypochlorous acid (C), which acts as a strong disinfectant.
Step-by-step explanation:
When chlorine gas is mixed with water, it reacts to form hypochlorous acid, a strong oxidant that is an effective disinfectant. Therefore, the correct answer to the question "Chlorine reacts with water to form what disinfectant?" is C) Hypochlorous acid. Chlorine gas, sodium hypochlorite, and calcium hypochlorite are known for their disinfectant properties and are used in various industries, including water treatment and food processing. Hypochlorous acid, generated from the reaction of chlorine with water, is responsible for the antimicrobial effect in drinking water supplies and swimming pools.