To determine which statement is correct regarding the percentage of existing species that are extinct, we can analyze the provided options step by step.
### Step-by-Step Solution:
1. **Understanding Extinction**:
- Extinction refers to the complete disappearance of a species from Earth. Once a species is extinct, it no longer exists anywhere in the world.
2. **Reviewing the Options**:
- The options provided are:
- A) 99% of existing species are extinct.
- B) 25% of existing species are extinct.
- C) 40% of existing species are extinct.
- D) 30% of existing species are extinct.
3. **Analyzing the First Option (A)**:
- The claim that 99% of existing species are extinct suggests that almost all species that have ever existed are no longer present. This statement seems exaggerated and not supported by scientific evidence.
4. **Analyzing the Other Options (B, C, D)**:
- The percentages provided in options B (25%), C (40%), and D (30%) all suggest a significantly lower proportion of extinct species compared to option A.
5. **Fact-Checking Extinction Rates**:
- Scientific studies suggest that while many species have gone extinct throughout Earth's history, the percentage of species that are currently extinct is generally estimated to be much lower than 99%. Estimates vary, but many suggest that around 1% to 10% of species may be extinct at any given time, depending on the specific context and time frame considered.
6. **Conclusion**:
- Given the analysis, option A (99% of existing species are extinct) is likely incorrect. The other options (B, C, D) present lower percentages, which are more plausible. However, without specific data, it is difficult to definitively state which of B, C, or D is correct based on the information provided.
7. **Final Answer**:
- Based on the analysis, the correct answer is that option A is incorrect, and the correct percentage of extinct species is likely much lower than 99%.
