Which one of the following sets of elements is called aerogen ?

Options

A. He,Ne,Ar
B. F,CI,Br
C. O,S,Se
D. N,P,As

Explanation

To determine which set of elements is called "aerogen," we need to analyze the options provided and identify the elements that are gases present in the atmosphere.

### Step-by-Step Solution:

1. **Understand the term "aerogen":**
- Aerogen refers to gases that are found in the atmosphere.

2. **Analyze each option:**
- **Option A: Helium, Neon, Argon**
- All three elements are noble gases and are present in the atmosphere. Helium and Neon are trace gases, while Argon is present at about 0.9% of the atmosphere.
- **Option B: Fluorine, Chlorine, Bromine**
- Fluorine and Chlorine are gases, but Bromine is a liquid at room temperature and not typically found in the atmosphere.
- **Option C: Oxygen, Sulphur, Selenium**
- Oxygen is a major component of the atmosphere (about 21%), but Sulphur and Selenium are not present in significant amounts in the atmosphere.
- **Option D: Nitrogen, Phosphorus, Antimony**
- Nitrogen is a major component of the atmosphere (about 78%), but Phosphorus and Antimony are not present in the atmosphere.

3. **Conclusion:**
- Based on the analysis, **Option A (Helium, Neon, Argon)** is the correct answer because all these elements are gases that are present in the atmosphere and thus classified as aerogens.

### Final Answer:
**The set of elements called aerogen is Option A: Helium, Neon, Argon.**

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