The eggs of some mammals have more yolk. They are

Options

A. Aquatic mammals
B. Metatherians
C. Protherians
D. Eutherians.

Answer

**Step-by-Step Solution:**

1. **Understanding Egg Classification**: Eggs are classified based on the amount of yolk they contain. The categories include:
- **Alecithal**: No yolk (e.g., human and placental mammals).
- **Microlecithal**: Minimal yolk (e.g., echinoderms and marsupials).
- **Mesolecithal**: Moderate yolk (e.g., amphibians).
- **Macrolecithal**: Large amount of yolk (e.g., birds and protherians).

2. **Identifying the Mammals with More Yolk**: The question specifically asks about mammals that have eggs with more yolk. Based on the classifications:
- Protherians (monotremes) are known to have macrolecithal eggs, which contain a large amount of yolk.

3. **Evaluating the Options**:
- **A. Aquatic mammals**: Generally have less yolk.
- **B. Metatherians**: (marsupials) have microlecithal eggs with minimal yolk.
- **C. Protherians**: (monotremes) have macrolecithal eggs with a large amount of yolk.
- **D. Eutherians**: (placental mammals) have alecithal eggs with no yolk.

4. **Conclusion**: Based on the classification and the characteristics of the eggs, the correct answer is **C. Protherians**.

**Final Answer**: The eggs of some mammals that have more yolk are **C. Protherians**.

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