All amniotes

Options

A. have 10 pairs of cranial nerves
B. have two pairs of limbs
C. lay cleidoic eggs
D. show internal fertilization

Answer

### Step-by-Step Solution:

1. **Understanding Amniotes**:
- Amniotes are a group of vertebrates that develop embryos within an amnion, which is a fluid-filled sac. This group includes birds, reptiles, and mammals.

2. **Analyzing the Options**:
- We need to evaluate each option provided in the question to determine which statement is true for all amniotes.

3. **Option 1: Have 10 pairs of cranial nerves**:
- This statement is incorrect. Amniotes actually have 12 pairs of cranial nerves, not 10.

4. **Option 2: Have two pairs of limbs**:
- This statement is also incorrect. While some amniotes (like mammals) have two pairs of limbs, reptiles can have four limbs. Therefore, this statement does not apply to all amniotes.

5. **Option 3: Leisleodic eggs**:
- This statement is incorrect as well. Only birds lay eggs that are considered leisleodic. Mammals typically give birth to live young, and not all reptiles lay eggs.

6. **Option 4: Internal fertilization**:
- This statement is correct. Most amniotes, including birds, reptiles, and mammals, undergo internal fertilization, meaning fertilization occurs inside the female's body.

7. **Conclusion**:
- The correct answer is that all amniotes undergo internal fertilization.

### Final Answer:
All amniotes have internal fertilization.

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