Which of the following is the earliest era

Options

A. Coenozoic
B. Mesozoic
C. Palaeozoic
D. Pre-cambrian.

Answer

To determine which of the following is the earliest era, we need to analyze the geological time scale and the options provided: Cenozoic, Mesozoic, Paleozoic, and Precambrian.

### Step-by-Step Solution:

1. **Understanding Geological Time Scale**:
- The geological time scale is a system that categorizes Earth's history into different segments, including eons, eras, periods, and epochs.

2. **Identifying the Options**:
- The options given are:
- Cenozoic
- Mesozoic
- Paleozoic
- Precambrian

3. **Defining Each Era**:
- **Cenozoic Era**: This is the most recent era, starting around 66 million years ago and continuing to the present.
- **Mesozoic Era**: This era follows the Paleozoic and spans from about 252 million years ago to 66 million years ago.
- **Paleozoic Era**: This era precedes the Mesozoic and ranges from about 544 million years ago to 252 million years ago.
- **Precambrian Era**: This era encompasses all geological time before the Paleozoic, starting from the formation of the Earth about 4.5 billion years ago to 544 million years ago.

4. **Determining the Earliest Era**:
- Since the Precambrian era includes the time from the formation of the Earth up to the beginning of the Paleozoic era, it is the earliest era among the options provided.

5. **Conclusion**:
- Therefore, the correct answer is **Precambrian** as it is the earliest era in the geological time scale.

### Final Answer:
The earliest era is **Precambrian**.