28. Water treatment includes water purification, disinfection, distillation, etc.Common water treatment agents include chlorine, ozone, bleach, activated carbon,etc. Swimming pools commonly use ozone and activated carbon to disinfect andpurify the pools. Which of the following statements is correct?
(A)The principles of ozone and activated carbon treatment are the same.
(B)Chlorine is a common disinfectant and the water disinfected with chlorine canbe directly used to prepare chemical reagents.
(C)Both chlorine and sulfur dioxide have bleaching properties, and mixing the twoin equal volumes will increase the efficiency of bleaching.
(D)Bleaching powder will be ineffective when left in the air for a long time.
(E)The most important ingredient of bleaching powder is CaCl2.