According to one of the most widely accepted theories, earth's atmosphere before origin of life was.

Options

A. oxidising
B. oxidising along with `H_(2)`
C. reducing with free `O_(2)` in small amont
D. reducing with oxygen absent in `O_(2)` form.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the composition of Earth's atmosphere before the origin of life, according to one of the most widely accepted theories.

2. **Identifying Early Earth Conditions**: It is important to recognize that the conditions on early Earth were vastly different from those today. The atmosphere was not conducive to life as we know it.

3. **Describing the Atmospheric Composition**: The early Earth's atmosphere was characterized by a reducing environment. This means that it lacked free oxygen (O2), which is essential for aerobic life forms.

4. **Listing the Major Gases**: The atmosphere primarily consisted of gases such as methane (CH4), ammonia (NH3), water vapor (H2O), and hydrogen (H2). These gases contributed to a highly reactive and unstable environment.

5. **Conclusion**: Based on the analysis, the correct answer is that the Earth's atmosphere before the origin of life was a reducing atmosphere, rich in methane, ammonia, water vapor, and hydrogen, but devoid of free oxygen.

**Final Answer**: The Earth's atmosphere before the origin of life was a reducing atmosphere, primarily composed of methane, ammonia, water vapor, and hydrogen, with no free oxygen present.

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