According to Oparin, which one of the following was not present in the primitive atmosphere of the earth?

Options

A. Methane
B. Oxygen
C. Hydrogen
D. Water vapour

Explanation

To answer the question "According to Oparin, which one of the following was not present in the primitive atmosphere of the earth?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Oparin's Hypothesis**: Oparin proposed a theory regarding the origin of life, suggesting that life originated from simple organic compounds in a primitive atmosphere through a series of chemical reactions.

2. **Identifying Components of Primitive Atmosphere**: According to Oparin, the primitive atmosphere was composed of various gases, including methane (CH₄), ammonia (NH₃), hydrogen (H₂), and water vapor (H₂O).

3. **Recognizing the Role of Oxygen**: Oparin's theory emphasizes that the primitive atmosphere was a reducing environment, meaning it lacked free oxygen. Oxygen is known to be an oxidizing agent, which would hinder the formation of organic compounds necessary for life.

4. **Conclusion**: Since oxygen was not present in the primitive atmosphere according to Oparin's hypothesis, it is the correct answer to the question.

5. **Final Answer**: Therefore, the answer to the question is that **oxygen** was not present in the primitive atmosphere of the earth according to Oparin.