Which one of the following gases present in the upper atmosphere cuts off a major portion of ultraviolet radiation of the sun from reaching the earth?

Options

A. Carbon dioxide
B. Ozone
C. Nitrogen
D. Oxygen

Answer

To answer the question, "Which one of the following gases present in the upper atmosphere cuts off a major portion of ultraviolet radiation of the sun from reaching the earth?", we can follow these steps:

### Step 1: Identify the gases listed
The options provided are:
1. Carbon Dioxide (CO₂)
2. Ozone (O₃)
3. Nitrogen (N₂)
4. Oxygen (O₂)

### Step 2: Understand the role of each gas
- **Carbon Dioxide (CO₂)**: Primarily known for its role in the greenhouse effect and does not significantly absorb ultraviolet (UV) radiation.
- **Ozone (O₃)**: Located in the stratosphere, ozone is known for its ability to absorb the majority of the sun's harmful ultraviolet radiation.
- **Nitrogen (N₂)**: Makes up a large portion of the atmosphere but does not absorb UV radiation effectively.
- **Oxygen (O₂)**: While it does absorb some UV radiation, its effect is not as significant as that of ozone.

### Step 3: Determine which gas is most effective in blocking UV radiation
From the understanding of the roles of these gases, we can conclude that:
- Ozone (O₃) is the gas that effectively absorbs and blocks a significant portion of the sun's harmful ultraviolet radiation.

### Step 4: Final answer
Thus, the correct answer is **Ozone (O₃)**.

---