Ozone is an unstable, dark blue diamagnetic gas. It absorbs strongly the UV radiation, thus proteching the people on the earth from the harmful UV radiation from the sun. The use of chloroflurocarbon (CFC) in aeroslos and refrigrators, and their subsequent escape into the atomsphere, is blamond for making holes in the ozone layer over the Antarctic, and Arctic.
Ozone acts as a strong oxdising agent in acidic and alkaline medium. For this property ozone is used as a germicide and disinfectant for sterillising water and improving the atmosphere of croweded places.
Identify the incorrect statement with respect to ozone.

Options

A. Ozone is formed in the upper atmosphere by a photochemical reaction involving dioxygen.
B. Ozone protects the earth's inhabitants by absorbing UV radiations.
C. Ozone can also be made by heating `O_(2)` over `2500^(circ)C`. And quenching.
D. Chloride gas is prefered over zone for the purification of drinking water and for water treatment in swimming pools.

Explanation

To identify the incorrect statement regarding ozone, let's analyze each statement step by step:

1. **Statement A: Ozone is formed in the upper atmosphere by a photochemical reaction involving dioxygen.**
- This statement is **true**. Ozone (O₃) is indeed formed in the upper atmosphere through photochemical reactions, primarily involving ultraviolet (UV) radiation that splits dioxygen (O₂) molecules, leading to the formation of ozone.

2. **Statement B: Ozone protects the earth's inhabitants by absorbing ultraviolet radiation.**
- This statement is also **true**. Ozone plays a crucial role in protecting life on Earth by absorbing the majority of the sun's harmful ultraviolet radiation, thus preventing it from reaching the surface.

3. **Statement C: Ozone can also be premade by heating oxygen over 2500 degrees centigrade and quenching.**
- This statement is **false**. Ozone is not typically formed by heating oxygen to such high temperatures. Instead, ozone is usually generated through a process called silent electric discharge, where electrical energy is used to convert dioxygen into ozone. The temperature mentioned (2500 degrees centigrade) is not a standard method for ozone production.

4. **Statement D: Chlorine gas is preferred over ozone for the purification of drinking water and for water treatment in swimming pools.**
- This statement is **true**. While ozone is an effective disinfectant, chlorine is often preferred in water treatment due to its lower cost and ease of use. However, ozone does not leave harmful by-products, making it a better option in some scenarios, but the installation and operation costs of ozone systems can be high.

Based on the analysis, the incorrect statement is **Statement C**.

### Summary of the Solution:
- Statement A: True
- Statement B: True
- Statement C: False (Incorrect)
- Statement D: True

### Conclusion:
The incorrect statement regarding ozone is **Statement C**.