A living fossil is

Options

A. Pinus
B. Ephedra
C. Cedrus
D. Cycas.

Answer

**Step-by-Step Solution:**

1. **Understanding the Term "Living Fossil":**
- A living fossil refers to an organism that has remained relatively unchanged from earlier geological times and has close relatives that are extinct. These organisms provide insight into the evolutionary history of life on Earth.

2. **Analyzing the Options:**
- The question provides four options: Pinus, Ephedra, Cedrus, and Cyclus. We need to determine which of these is considered a living fossil.

3. **Evaluating Each Option:**
- **Pinus:**
- Pinus is the largest genus of conifers and is prevalent in the northern hemisphere. It has undergone changes and adaptations over time, so it does not qualify as a living fossil.
- **Ephedra:**
- Ephedra is known for its medicinal properties, particularly the compound ephedrine. It does not represent a lineage that has remained unchanged, thus it is not a living fossil.
- **Cedrus:**
- Cedrus belongs to the family Pinaceae. Similar to Pinus, it has evolved and does not fit the definition of a living fossil.
- **Cyclus:**
- Cyclus is recognized as a living fossil because it produces seeds but not flowers. It has persisted through geological time with minimal changes, making it the correct answer.

4. **Conclusion:**
- After evaluating all the options, the correct answer to the question "A living fossil is" is **Cyclus**.

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