Which one of the following is categorised under living fossils?

Options

A. Pinus
B. Cycas
C. Selaginella
D. Taxus

Answer

To determine which of the following options is categorized under living fossils, we will analyze each option provided: Penis, Cyclus, Selanganella, and Taxus.

### Step-by-Step Solution:

1. **Understanding Living Fossils**:
- Living fossils are organisms that have remained relatively unchanged over millions of years and resemble their ancient ancestors. They provide insight into the evolutionary history of life on Earth.

2. **Analyzing Each Option**:
- **Penis**: This appears to be a typographical error and likely refers to "Pinus," which is the genus of pine trees. While they are ancient, they do not fit the strict definition of living fossils.
- **Cyclus**: This is likely referring to "Cycads," specifically the genus Cycas. Cycads are indeed considered living fossils because they have existed for millions of years and have retained many primitive characteristics.
- **Selanganella**: This refers to the genus Selaginella, which includes species that resemble club mosses. While they are ancient plants, they do not fit the definition of living fossils as closely as Cycas.
- **Taxus**: This is the genus of yew trees. They are also ancient but do not exhibit the same level of unchanged characteristics over millions of years as Cycas.

3. **Conclusion**:
- After analyzing all options, **Cycus (Cycads)** is categorized under living fossils because it has remained relatively unchanged for millions of years and retains characteristics of ancient plants.

### Final Answer:
The correct answer is **Cycus**.