Which is called a hidden gas ?

Options

A. Xe
B. He
C. Kr
D. Rn

Answer

To determine which gas is referred to as a "hidden gas," we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Options**: The question provides four options:
- A) Xe (Xenon)
- B) He (Helium)
- C) Kr (Krypton)
- D) Rn (Radon)

2. **Understand the Context**: The term "hidden gas" suggests a connection to the meaning of the name of the gas.

3. **Research the Names**:
- **Xenon (Xe)**: The name does not imply anything related to being hidden.
- **Helium (He)**: The name is derived from the Greek word for the sun (helios), not related to hidden.
- **Krypton (Kr)**: The name comes from the Greek word "kryptos," which means "hidden."
- **Radon (Rn)**: The name is derived from radium, and does not imply hiddenness.

4. **Conclusion**: Based on the meanings of the names, Krypton (Kr) is derived from the Greek word "kryptos," which means "hidden." Therefore, Krypton is referred to as the "hidden gas."

### Final Answer:
Krypton (Kr) is called a hidden gas.

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