One of the following features in aves may not be considered as a contributory factor in reducing the weight of body

Options

A. Presence of single ovary
B. Presence of pneumatic bones
C. Absence of urinary bladder
D. Presence of four chambered heart

Answer

To solve the question regarding which feature in Aves (birds) may not be considered a contributory factor in reducing body weight, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: We need to identify which feature of birds does not contribute to reducing their body weight, which is essential for flight.

2. **List the Features**: The options provided typically include:
- Presence of single ovaries
- Presence of pneumatic (hollow) bones
- Absence of urinary bladder
- Presence of a four-chambered heart

3. **Analyze Each Feature**:
- **Single Ovaries**: Birds typically have only one functional ovary, which reduces weight and aids in flight. This feature contributes to weight reduction.
- **Pneumatic Bones**: These are hollow bones that are lighter than solid bones, significantly contributing to weight reduction for flight.
- **Absence of Urinary Bladder**: Birds excrete waste in a more efficient manner without a urinary bladder, which also reduces weight.
- **Four-Chambered Heart**: While this feature is crucial for efficient circulation and oxygen delivery, it does not directly contribute to reducing body weight.

4. **Conclusion**: Among the options, the presence of a four-chambered heart is the feature that may not be considered a contributory factor in reducing body weight.

### Final Answer:
The presence of a four-chambered heart.