During the days of Dinosaurs, mammals had

Options

A. Already evolved
B. A size of rats and mice
C. Both A and B
D. Not yet evolved.

Answer

**Step-by-Step Solution:**

1. **Understanding the Time Period**: The question refers to the time when dinosaurs existed, primarily during the Jurassic period. It's important to clarify the timeline of dinosaurs and mammals.

2. **Identifying the Era of Dinosaurs**: Dinosaurs first appeared in the Triassic period, and they became prominent during the Jurassic period. This is crucial for understanding the evolution of mammals in relation to dinosaurs.

3. **Evolution of Mammals**: During the Triassic period, the earliest mammals were present, which were egg-laying mammals. This indicates that mammals had already evolved before the Jurassic period.

4. **Mammals in the Jurassic Period**: By the time of the Jurassic period, mammals had diversified and included larger species. This counters the idea that they were only the size of rats and mice.

5. **Evaluating the Options**:
- **Option A**: "Already evolved" - This is correct as mammals had evolved by the time of the dinosaurs.
- **Option B**: "Size of rats and mice" - This is incorrect because mammals were larger and more diverse during this period.
- **Option C**: "Both A and B" - This is incorrect since Option B is wrong.
- **Option D**: "Not yet evolved" - This is also incorrect as mammals had already evolved.

6. **Conclusion**: The correct answer is Option A: "Already evolved."

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