Which of these is not a mammal ?

Options

A. Dolphin
B. Shark
C. Seal
D. Whale

Explanation

**Step-by-Step Solution:**

1. **Identify the Options**: The question presents four options: dolphin, shark, seal, and whale. We need to determine which of these is not a mammal.

2. **Understand Mammal Characteristics**: Mammals are warm-blooded animals that typically have hair or fur, and they give live birth (with some exceptions) and produce milk to feed their young.

3. **Analyze Each Option**:
- **Dolphin**: Dolphins are warm-blooded, have a layer of blubber, and are known to nurse their young with milk. Therefore, dolphins are mammals.
- **Shark**: Sharks are cold-blooded fish that lay eggs or give live birth but do not produce milk or have fur. Therefore, sharks are not mammals.
- **Seal**: Seals are warm-blooded, have fur, and also nurse their young. Hence, seals are mammals.
- **Whale**: Whales are warm-blooded, have blubber instead of fur, and give live birth while nursing their young. Thus, whales are mammals.

4. **Conclusion**: Among the options provided, the shark is the only one that does not fit the characteristics of mammals. Hence, the answer to the question is the shark.

**Final Answer**: The shark is not a mammal.

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