Study the following statements about ozone :
(a) It is essential for breathing of living organisms.
(b) It is used to disinfect water.
(c ) It absorbs ultraviolet rays.
(d) Its proportion in air is about 3%.
Which of these statements are correct ?

Options

A. (a), (b) and (c )
B. (b) and (c )
C. (a) and (d)
D. All four

Answer

To determine which statements about ozone are correct, let's analyze each statement one by one:

1. **Statement (a)**: "It is essential for breathing of living organisms."
- Ozone (O3) is not directly used for breathing by living organisms. Instead, it is oxygen (O2) that is essential for breathing. Ozone does play a crucial role in the atmosphere by forming a layer that protects living organisms from harmful ultraviolet (UV) rays. Therefore, this statement is **incorrect**.

2. **Statement (b)**: "It is used to disinfect water."
- Ozone is indeed used to disinfect water. This process is known as ozonation, where ozone is mixed with water to kill bacteria and other pathogens. Thus, this statement is **correct**.

3. **Statement (c)**: "It absorbs ultraviolet rays."
- Ozone in the stratosphere absorbs a significant amount of UV radiation from the sun, protecting living organisms on Earth from harmful effects. Therefore, this statement is **correct**.

4. **Statement (d)**: "Its proportion in air is about 3%."
- The proportion of ozone in the atmosphere is much lower than 3%. In fact, it constitutes only about 0.000004% of the atmosphere. Thus, this statement is **incorrect**.

Based on the analysis:
- **Correct Statements**: (b) and (c)
- **Incorrect Statements**: (a) and (d)

### Final Answer:
The correct statements about ozone are (b) and (c).