To solve the question regarding heat transfer in a closed room, we will analyze the different modes of heat transfer: conduction, convection, and radiation.
### Step-by-Step Solution:
1. **Understanding Heat Transfer Modes**:
- Heat transfer can occur through three primary modes: conduction, convection, and radiation.
- Conduction occurs through direct contact between materials, convection involves the movement of fluids (liquids or gases), and radiation involves the transfer of heat through electromagnetic waves.
2. **Analyzing Conduction**:
- In a closed room filled with air, conduction is generally minimal because air is a poor conductor of heat.
- Conduction requires a medium where particles are in direct contact, and since air is a gas, the conduction is negligible compared to other modes.
3. **Analyzing Convection**:
- Convection occurs in fluids (liquids and gases) when there is a difference in temperature and density.
- In a closed room, if the air inside is warmer than the air outside, the warmer air (which is less dense) will rise, and the cooler air (which is denser) will sink. This creates a convection current.
- Therefore, convection is a significant mode of heat transfer in a closed room.
4. **Analyzing Radiation**:
- Radiation can occur in a closed room, but its effectiveness depends on the temperature difference and the surfaces involved.
- In a typical closed room, the amount of heat transferred by radiation is relatively less compared to convection, especially if the temperature difference is not significant.
5. **Conclusion**:
- Given that conduction is negligible and radiation is minimal, the primary mode of heat transfer in a closed room is convection.
- Therefore, the correct answer to the question is **B: Convection**.
### Final Answer:
The heat transfer in a closed room takes place primarily by **convection**.
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