The correct answer is A. Chlorination.
Chlorination is the most common method of water purification. It is a simple, effective, and inexpensive way to kill harmful bacteria and viruses in water. Chlorine is added to water in the form of chlorine gas, sodium hypochlorite, or calcium hypochlorite. The chlorine reacts with organic matter in the water to form chloramines, which are also effective at killing bacteria and viruses.
Chlorination is not without its drawbacks, however. Chlorine can react with other chemicals in water to form harmful byproducts, such as trihalomethanes (THMs). THMs have been linked to an increased risk of cancer. Chlorine can also cause taste and odor problems in water.
Despite its drawbacks, chlorination is still the most common method of water purification. It is a safe and effective way to kill harmful bacteria and viruses in water.
B. Distillation is a process of purification that involves boiling water and then condensing the steam back into liquid form. This process removes dissolved minerals and other impurities from the water. Distillation is a very effective method of water purification, but it is also very energy-intensive.
C. Filtration is a process of purification that involves passing water through a filter to remove particles and other impurities. Filters can be made of a variety of materials, including paper, cloth, and activated carbon. Filtration is a less effective method of water purification than chlorination or distillation, but it is also less expensive and less energy-intensive.
D. Decantation is a process of purification that involves allowing water to stand so that the impurities settle to the bottom. The clear water can then be poured off the top. Decantation is a very simple and inexpensive method of water purification, but it is also the least effective.