Number of aeons in geological time scale is

Options

A. 3
B. 5
C. 7
D. 9

Answer

To determine the number of aeons in the geological time scale, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Aeons**: An aeon is the largest division of geological time, and it encompasses significant periods in Earth's history.

2. **Identifying the Aeons**: There are three recognized aeons in the geological time scale:
- **Phanerozoic Eon**: This is the most recent eon, characterized by abundant fossil evidence and the emergence of complex life.
- **Proterozoic Eon**: This eon precedes the Phanerozoic and is marked by the development of simple life forms and significant geological changes.
- **Archean Eon**: This is the oldest eon, during which the Earth’s crust cooled and the first simple life forms appeared.

3. **Counting the Aeons**: Based on the definitions and classifications, we can count the aeons:
- **1st Aeon**: Archean
- **2nd Aeon**: Proterozoic
- **3rd Aeon**: Phanerozoic

4. **Conclusion**: Therefore, the total number of aeons in the geological time scale is **3**.

### Final Answer:
The number of aeons in the geological time scale is **3**.

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