Which of the following group of animals have a constant body temperature?

Options

A. Reptiles, aves & mammalia
B. Aves & cyclostomata
C. Pisces & amphibia
D. Aves & mammalia

Answer

To determine which group of animals has a constant body temperature, we need to understand the concepts of warm-blooded and cold-blooded animals.

### Step-by-Step Solution:

1. **Identify the Options**: The question provides four options to choose from. We need to analyze each option to see which group of animals maintains a constant body temperature.

2. **Analyze Option 1**: The first option includes reptiles, apes, and mammals.
- Reptiles are cold-blooded animals, meaning their body temperature fluctuates with the environment.
- Apes and mammals are warm-blooded.
- Since reptiles are included, this option is incorrect.

3. **Analyze Option 2**: The second option includes apes and cyclostomes.
- Cyclostomes (like lampreys and hagfish) are also cold-blooded.
- Since cyclostomes do not maintain a constant body temperature, this option is incorrect.

4. **Analyze Option 3**: The third option includes Pisces (fish) and amphibians.
- Both Pisces and amphibians are cold-blooded animals.
- Their body temperatures vary with the surrounding environment, making this option incorrect.

5. **Analyze Option 4**: The fourth option includes apes and mammals.
- Both apes and mammals are warm-blooded (endothermic) animals.
- They have a constant body temperature that is independent of environmental conditions.
- Therefore, this option is correct.

6. **Conclusion**: The group of animals that have a constant body temperature is found in option 4, which includes apes and mammals.

### Final Answer:
The correct answer is **Option 4: Apes and Mammals**.

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