Life has existed on earth for the last

Options

A. 2.3 billion years
B. 3.9 billion years
C. 4.3 billion years
D. 5.0 billion years

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks how long life has existed on Earth. We need to determine the approximate time frame based on scientific evidence.

2. **Determine Earth's Age**: Earth is estimated to have formed about 4.54 billion years ago. This gives us a starting point for understanding the timeline of life on Earth.

3. **Identify Earliest Signs of Life**: According to scientific research, the earliest signs of life on Earth date back to approximately 3.5 billion years ago. This is based on fossil evidence that has been dated to this time.

4. **Evaluate the Options**: The options provided are:
- A) 2.3 billion years
- B) 3.9 billion years
- C) 4.3 billion years
- D) 5 billion years

5. **Analyze Each Option**:
- Option A (2.3 billion years) is too early and not supported by fossil evidence.
- Option D (5 billion years) is also too early, as Earth itself is only about 4.54 billion years old.
- Options B (3.9 billion years) and C (4.3 billion years) are closer to the estimated age of the earliest life forms.

6. **Select the Closest Option**: Since the earliest evidence of life is around 3.5 billion years ago, the closest option provided is B (3.9 billion years). Therefore, we conclude that life has existed on Earth for approximately 3.9 billion years.

7. **Final Answer**: The answer to the question is that life has existed on Earth for the last **3.9 billion years**.