Which of the following was used as an energy source by Miller in his experiment?

Options

A. UV radiation
B. Oxygen
C. Condenser
D. Electric discharge

Answer

### Step-by-Step Solution:

1. **Understanding the Experiment**: Miller conducted an experiment to explore the origin of life on Earth. He aimed to simulate the conditions of early Earth to see if organic compounds could be formed.

2. **Components Used**: In his experiment, Miller used a mixture of gases that were thought to represent the early Earth's atmosphere. These gases included methane (CH₄), ammonia (NH₃), hydrogen (H₂), and water (H₂O).

3. **Energy Source**: To mimic the energy that might have been available on early Earth, Miller introduced a continuous discharge of electric current into the system. This was meant to simulate lightning strikes, which were believed to be common in the early atmosphere.

4. **Conclusion**: After conducting the experiment, Miller analyzed the products formed using chromatography. The key point here is that the energy source used by Miller was the electric discharge.

5. **Final Answer**: Therefore, the correct answer to the question "Which of the following was used as an energy source by Miller in his experiment?" is **electric discharge**.