Two chief features of mammals which distinguish them from other vertebrates are:

Options

A. Hairy skin and ovipary
B. Mammary glands and hairs
C. Pinna and teeth
D. Teeth and mammary glands

Answer

To answer the question regarding the two chief features of mammals that distinguish them from other vertebrates, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Class Mammalia**:
- Mammals belong to the class Mammalia, which is characterized by specific features that set them apart from other vertebrates.

2. **Recognize Key Features of Mammals**:
- There are several distinguishing features of mammals. Among these, two primary characteristics stand out.

3. **Feature 1: Mammary Glands**:
- One of the most significant features of mammals is the presence of mammary glands. These glands produce milk, which is used to nourish their young. This is a unique trait not found in other vertebrate classes.

4. **Feature 2: Hair or Fur**:
- Another defining characteristic of mammals is that their bodies are covered with hair or fur. This feature helps in insulation and protection, which is distinct from other vertebrates that may have scales or feathers.

5. **Conclusion**:
- Therefore, the two chief features that distinguish mammals from other vertebrates are the presence of mammary glands and the presence of hair.

### Final Answer:
The two chief features of mammals that distinguish them from other vertebrates are:
1. Mammary glands (milk-producing glands).
2. Hair or fur covering their bodies.

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