The formation of `O_3` in upper part of atmosphere is catalyzed by

Options

A. `N_2`
B. `NO`
C. CO
D. `CO_2`

Answer

To determine which substance catalyzes the formation of ozone (O3) in the upper atmosphere, we can follow these steps:

### Step-by-Step Solution

1. **Understand the Role of Ozone**:
- Ozone (O3) is a molecule that forms a layer in the upper atmosphere, which protects the Earth from harmful ultraviolet (UV) radiation from the sun.

2. **Identify the Reaction for Ozone Formation**:
- Ozone is formed from molecular oxygen (O2) in the presence of certain catalysts and under specific conditions, such as exposure to bright light.

3. **Consider the Given Options**:
- The options provided are N2, NO, CO, and CO2. We need to identify which of these substances acts as a catalyst in the formation of ozone.

4. **Recall the Catalytic Process**:
- The formation of ozone can occur through a reaction involving nitrogen dioxide (NO2) and molecular oxygen (O2) when exposed to bright sunlight.
- In this process, nitric oxide (NO) plays a crucial role as a catalyst.

5. **Conclude the Correct Answer**:
- Based on the catalytic role of NO in the formation of ozone, we conclude that the formation of O3 in the upper part of the atmosphere is catalyzed by NO.

### Final Answer:
The formation of O3 in the upper part of the atmosphere is catalyzed by **NO** (Nitric Oxide).

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