First life on the Earth were:

Options

A. autotrophs
B. cyanobacteria
C. photoautotrophs
D. chemoheterotrophs

Answer

### Step-by-Step Solution:

1. **Understanding the First Life Forms**: The question asks about the first life forms on Earth. It is important to recognize that these were microorganisms, specifically bacteria.

2. **Conditions of Early Earth**: The early Earth had a very different atmosphere compared to today. Notably, it lacked oxygen. This absence of oxygen is crucial in determining the type of organisms that could survive and thrive.

3. **Role of Oxygen**: Since oxygen was not present in the atmosphere, the first life forms would not have relied on oxygen for their metabolic processes. Instead, they would have utilized other inorganic materials to obtain energy.

4. **Types of Early Life Forms**: The first life forms were likely chemoheterotrophs. Chemoheterotrophs are organisms that obtain their energy by consuming organic compounds, which they derive from other organisms or inorganic matter.

5. **Evolution of Other Life Forms**: Following the emergence of chemoheterotrophs, autotrophs evolved. Autotrophs are organisms that can produce their own food, either through photosynthesis (photo-autotrophs) or chemosynthesis (chemo-autotrophs).

6. **Conclusion**: Based on the understanding of early life forms and their metabolic processes, the first life on Earth can be classified as chemoheterotrophs.

### Final Answer:
The first life on Earth were **chemoheterotrophs**.

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