The process which can transfer heat through the vacuum as well as air is :

Options

A. conduction
B. convection
C. irradiation
D. radiation

Answer

To solve the question, "The process which can transfer heat through the vacuum as well as air is:", we will analyze the options given and determine which one fits the criteria of transferring heat in both mediums.

### Step-by-Step Solution:

1. **Understand the Types of Heat Transfer**:
- There are three main methods of heat transfer: conduction, convection, and radiation.

2. **Define Conduction**:
- Conduction is the transfer of heat through a solid material without the movement of the material itself. It requires direct contact between molecules.

3. **Define Convection**:
- Convection is the transfer of heat through fluids (liquids and gases) due to the movement of the fluid itself. It requires a medium (air or liquid) to transfer heat.

4. **Define Radiation**:
- Radiation is the transfer of heat in the form of electromagnetic waves. It does not require a medium and can occur through a vacuum (like space).

5. **Analyze the Options**:
- Since conduction requires a medium (solid), and convection requires a fluid (liquid or gas), neither can transfer heat through a vacuum.
- Radiation, on the other hand, can transfer heat through both vacuum (like the heat from the sun reaching Earth) and air.

6. **Conclusion**:
- The correct answer is **radiation**, as it is the only process that can transfer heat through both vacuum and air.

### Final Answer:
The process which can transfer heat through the vacuum as well as air is **radiation**.

---