Which of the following is not an adaptation shown by birds for flying?

Options

A. Most bones are hollow and light.
B. Hindlimbs are modified into wings to enable flight.
C. Body is covered with feathers.`
D. Breast muscles are strong.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks us to identify which adaptation is NOT shown by birds for flying. This means we need to evaluate the adaptations that birds have developed to assist them in flight.

2. **Reviewing the Options**: We need to analyze each option provided to determine if it is indeed an adaptation for flying or not.

3. **Analyzing the First Option**:
- The first option states that "most bones are hollow and light."
- This is true for birds, as they have pneumatic bones that reduce their weight, making it easier for them to fly.

4. **Analyzing the Second Option**:
- The second option mentions that "hind limbs are modified into wings to enable flight."
- This is incorrect because it is the forelimbs (not hind limbs) that are modified into wings in birds. Therefore, this option does not represent an adaptation for flying.

5. **Analyzing the Third Option**:
- The third option states that "the body is covered by feathers."
- This is a true adaptation as feathers are essential for flight, providing lift and aiding in aerodynamics.

6. **Analyzing the Fourth Option**:
- The fourth option mentions "the breast muscles are strong."
- This is also true, as strong breast muscles are crucial for the flapping motion needed for flight.

7. **Conclusion**: After analyzing all options, we conclude that the second option, which states that "hind limbs are modified into wings to enable flight," is the adaptation that is NOT shown by birds for flying.

**Final Answer**: The adaptation that is not shown by birds for flying is the second option: "hind limbs are modified into wings to enable flight."

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