The correct answer is option 2. This statement is not correct because bleaching powder does not act as a reducing agent in many chemical industries.

Let`s examine each option to understand why they are correct or incorrect:

Option 1 states that bleaching powder is prepared by the action of chlorine on dry slaked lime [Ca(OH)2], and this is correct. Bleaching powder is made by treating dry slaked lime with chlorine gas.

Option 2 is incorrect because bleaching powder does not act as a reducing agent in many chemical industries. Bleaching powder is primarily used as an oxidizing agent rather than a reducing agent. It is commonly used for disinfection purposes.

Option 3 states that bleaching powder is also known as chlorinated lime, and this is correct. Bleaching powder is another name for chlorinated lime because it contains chlorine.

Option 4 states that bleaching powder is used for disinfecting drinking water, and this is correct. Bleaching powder is commonly used as a disinfectant for drinking water because it can kill bacteria and viruses.

In conclusion, option 2 is the correct answer as it states something that is not true about bleaching powder.