Trilobites evolved in

Options

A. (a) precambrian
B. (b) ordovician
C. (c) silurian
D. (d) cambrian

Answer

**Step-by-Step Solution:**

1. **Understanding Trilobites**:
- Trilobites are marine arthropods that are among the earliest known members of the phylum Arthropoda. They are significant in the study of paleontology due to their well-preserved fossils.

2. **Identifying the Era**:
- To determine when Trilobites evolved, we need to look at the geological time scale and the major eras of Earth's history.

3. **Examining the Options**:
- The options provided include Pre-Cambrian, Cambrian, Ordovician, and Silurian eras.
- Pre-Cambrian is the earliest era, which predates the Cambrian and is characterized by the absence of complex life forms.
- The Ordovician era saw the emergence of primitive land plants.
- The Silurian era is known for the evolution of fishes.

4. **Finding the Correct Era**:
- Trilobites first appeared around 542 million years ago, which corresponds to the Cambrian era. This era is known for the "Cambrian Explosion," a time of rapid diversification of life.

5. **Conclusion**:
- Based on the information gathered, the correct answer to the question "Trilobites evolved in" is the Cambrian era.

**Final Answer**: Cambrian era (Option D).

---