The first mammals that evolved were

Options

A. Large sized and aquatic
B. Large sized and terrestrial
C. Small sized and fast running terrestrial forms
D. Vestigial organs

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Question**: The question asks about the first mammals that evolved. To answer this, we need to consider the characteristics of early mammals and their evolutionary context.

2. **Context of Evolution**: Early mammals evolved during a time when dinosaurs were dominant. However, the first mammals were not large like dinosaurs; instead, they were small-sized creatures.

3. **Characteristics of Early Mammals**: The first mammals were terrestrial, meaning they lived on land. They were small in size, which allowed them to be agile and fast-running. This size and agility were advantageous for survival in a world dominated by larger predators.

4. **Evolutionary Progression**: Over time, as evolution continued, mammals diversified and some evolved into larger forms. However, the initial mammals were characterized by their small size and ability to run quickly on land.

5. **Conclusion**: Based on the characteristics discussed, the first mammals that evolved were small-sized, fast-running terrestrial forms.

**Final Answer**: The first mammals that evolved were small-sized, fast-running terrestrial forms.

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