Which gas is used to improve the atmosphere of the crowded places ?

Options

A. `H_2`
B. `O_2`
C. `O_3`
D. `N_2 O`

Explanation

To solve the question about which gas is used to improve the atmosphere in crowded places, we can follow these steps:

### Step 1: Understand the Context
In crowded places, there is a higher population density, which leads to an increased demand for oxygen. This means that the atmosphere in such areas may become depleted in oxygen, necessitating a way to enhance the air quality.

**Hint:** Consider how population density affects air quality and the need for oxygen.

### Step 2: Analyze the Options
We have four options: H2 (hydrogen), O2 (oxygen), O3 (ozone), and N2O (nitrous oxide). We need to determine which of these gases can help improve the atmosphere in crowded places.

**Hint:** Think about the role of each gas in the atmosphere and its effects on air quality.

### Step 3: Evaluate Each Gas
- **H2 (Hydrogen):** While hydrogen is a fuel and can be used in energy production, it does not contribute to improving air quality in terms of oxygen levels.

- **O2 (Oxygen):** This is essential for respiration, but the question is about a gas that can actively improve the atmosphere, not just provide oxygen.

- **O3 (Ozone):** Ozone is known to decompose into oxygen (O2) and can help increase the availability of oxygen in the atmosphere. It also acts as a powerful oxidizing agent, which can help purify the air.

- **N2O (Nitrous Oxide):** This gas is primarily a greenhouse gas and does not contribute to improving air quality in the same way as ozone.

**Hint:** Focus on the gas that can actively convert into oxygen and has a purifying effect.

### Step 4: Conclusion
Based on the analysis, the gas that is used to improve the atmosphere in crowded places is **O3 (ozone)**. Ozone decomposes to produce oxygen and can enhance the air quality by increasing the availability of oxygen.

**Final Answer:** The gas used to improve the atmosphere of crowded places is **O3 (ozone)**.