Which of the following eras, in geological time scale corresponds to the period when life had not originated upon the earth?

Options

A. Azoic
B. Palaezoic
C. Mesozoic era
D. Archaeozic

Explanation

To determine which era in the geological time scale corresponds to the period when life had not originated upon the Earth, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Geological Time Scale**: The geological time scale is divided into eons, eras, and periods that represent the history of the Earth and the evolution of life.

2. **Identify the Eons**: The geological time scale includes several eons:
- **Azoic Eon**: This is the earliest eon, characterized by the absence of life.
- **Archeozoic Eon**: This eon marks the beginning of life with the emergence of simple, primitive organisms.
- **Proterozoic Eon**: This eon saw the development of more complex life forms.
- **Phanerozoic Eon**: This eon is significant for the diversification of life and is further divided into Paleozoic, Mesozoic, and Cenozoic eras.

3. **Analyze the Options**: The question provides options that likely include various eons and eras. We need to identify which of these corresponds to a time when life did not exist.

4. **Evaluate Each Option**:
- **Azoic Era**: This era corresponds to a time before life existed on Earth, around 4 to 4.5 billion years ago.
- **Archeozoic Eon**: Life began to emerge during this eon.
- **Proterozoic Eon**: Life continued to evolve and diversify.
- **Phanerozoic Eon**: Life was abundant and diversified significantly.

5. **Conclusion**: The only era where life had not originated is the **Azoic Era**. Therefore, the correct answer is **Option A**.