All mammals have all of the following traits, except

Options

A. Amnion
B. Chorion
C. Placenta
D. hair

Answer

**Step-by-Step Solution:**

1. **Understanding Mammalian Traits**: Mammals are characterized by several traits including the presence of hair, mammary glands, and specific reproductive structures.

2. **Identifying the Traits**: The traits mentioned in the question include:
- Amnion: An extra embryonic membrane providing a safe environment for the embryo.
- Chorion: Another extra embryonic membrane that protects the embryo from external shocks.
- Placenta: An organ that provides nutrients and oxygen to the developing fetus in most mammals.
- Hair: A characteristic feature found in all mammals.

3. **Analyzing Each Trait**:
- **Amnion**: Present in all mammals as it is crucial for embryo development.
- **Chorion**: Also present in all mammals, serving a protective function.
- **Placenta**: While it is found in most mammals, there are exceptions, particularly in egg-laying mammals like the Platypus and Echidna, which do not have a placenta.
- **Hair**: This trait is universally present in all mammals.

4. **Conclusion**: Since the placenta is not found in all mammals (specifically absent in egg-laying mammals), it is the correct answer to the question.

5. **Final Answer**: All mammals have all of the following traits, except the Placenta.

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