Which of the following is used in anesthesia ?

Options

A. `N_2`
B. `N_2O`
C. `CH_4`
D. `CO_2`

Answer

To determine which of the given options is used in anesthesia, we can analyze each option based on their properties and uses in medical practice.

### Step-by-Step Solution:

1. **Identify the Options**: The options provided are:
- A) N2 (Nitrogen)
- B) N2O (Nitrous Oxide)
- C) CH4 (Methane)
- D) CO2 (Carbon Dioxide)

2. **Understand the Role of Anesthetic Agents**: Anesthetic agents are substances that induce a state of controlled unconsciousness and insensitivity to pain during surgical procedures.

3. **Analyze Each Option**:
- **N2 (Nitrogen)**: Nitrogen is an inert gas and is not used as an anesthetic. It does not have anesthetic properties.
- **N2O (Nitrous Oxide)**: Nitrous oxide is commonly known as "laughing gas." It is a weak anesthetic and is often used in combination with other more potent anesthetic agents. It can be used in concentrations of about 70% with 30% oxygen for general anesthesia.
- **CH4 (Methane)**: Methane is a flammable gas and is not used in anesthesia. It does not have anesthetic properties.
- **CO2 (Carbon Dioxide)**: Carbon dioxide is a byproduct of respiration and is not used as an anesthetic. It can cause respiratory issues if inhaled in high concentrations.

4. **Conclusion**: Based on the analysis, the only option that is used in anesthesia is N2O (Nitrous Oxide).

### Final Answer:
The correct answer is **B) N2O (Nitrous Oxide)**.

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