Trilobites were dominant in

Options

A. Precambrian
B. Cambrian
C. Ordovician
D. both b and c

Answer

**Step-by-Step Solution:**

1. **Understanding Trilobites**: Begin by recognizing what trilobites are. They are a group of early arthropods that were highly successful and diverse, with many species recorded in the fossil record.

2. **Identifying the Era**: The question asks in which geological era trilobites were dominant. The options provided are Precambrian, Cambrian, Ordovician, and Botanian.

3. **Fossil Record**: It is important to note that the last fossils of trilobites are found in rocks that are about 250 million years old. This indicates that they were present and thriving before this time.

4. **Era of Dominance**: Trilobites were most successful during the Cambrian and Ordovician periods. However, they are primarily known for their dominance during the Cambrian period, which began around 540 million years ago.

5. **Conclusion**: Based on the information gathered, the era in which trilobites were dominant is the Cambrian period.

**Final Answer**: Cambrian

---