Which of the following statements is correct?

Options

A. Good ozone occurs naturally in the troposphere.
B. Nitrogen oxide is an example of suspended particulate matter or SPM.
C. `SO_2` combines with haemoglobin and affects the oxygen carrying capacity of the blood.
D. Chlorofluorocarbons are the major ozone depleting substances which produce active chlorine in the presence of UV radiations.

Answer

To determine which of the statements is correct, we will analyze each statement one by one based on the information provided in the video transcript.

### Step 1: Analyze Statement 1
**Statement 1:** Good ozone occurs naturally in the top of the sphere.

- **Analysis:** Good ozone is indeed found in the stratosphere, which is the second layer of the Earth's atmosphere. This layer contains the ozone layer that protects us from harmful UV radiation. Therefore, this statement is **correct**.

### Step 2: Analyze Statement 2
**Statement 2:** Nitrogen oxide is your suspended particulate matter.

- **Analysis:** This statement is **false**. Nitrogen oxides (NOx) are gases that contribute to air pollution but are not classified as suspended particulate matter. Suspended particulate matter consists of tiny particles or droplets in the air that can include dust, soot, and liquid droplets.

### Step 3: Analyze Statement 3
**Statement 3:** SO2 combines with hemoglobin and affects the oxygen-carrying capacity of the blood.

- **Analysis:** This statement is also **false**. Sulfur dioxide (SO2) does not combine with hemoglobin. Instead, it is carbon monoxide (CO) that binds with hemoglobin to form carboxyhemoglobin, which reduces the blood's ability to carry oxygen.

### Step 4: Analyze Statement 4
**Statement 4:** Chlorofluorocarbons are major ozone-depleting substances that produce active chlorine when exposed to UV radiation.

- **Analysis:** This statement is **correct**. Chlorofluorocarbons (CFCs) are indeed known to deplete the ozone layer. When CFCs are exposed to UV radiation, they release chlorine atoms, which can destroy ozone molecules.

### Conclusion
After analyzing all the statements:
- Statement 1 is correct.
- Statement 2 is false.
- Statement 3 is false.
- Statement 4 is correct.

The correct statements are **Statement 1 and Statement 4**.