Which is common trait of mammals

Options

A. Carnivores
B. Ventral nerve cord
C. Seven cranial nerves .
D. Seven cervical vertebrae.

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a common trait of mammals from the given options.

2. **Analyzing the Options**:
- **Option 1: Carnivore**: This option suggests that all mammals are carnivores. However, this is incorrect as mammals can be herbivores, omnivores, or carnivores.
- **Option 2: Ventral Nerve Cord**: Mammals have a dorsal nerve cord, not a ventral one. Therefore, this option is also incorrect.
- **Option 3: Seven Cranial Nerves**: While mammals do have cranial nerves, the number can vary, and this is not a defining trait of all mammals.
- **Option 4: Seven Cervical Vertebrae**: Most mammals possess seven cervical vertebrae, which is a common trait across the class Mammalia.

3. **Identifying the Correct Answer**: After evaluating all the options, the correct answer is **Option 4: Seven Cervical Vertebrae**. This trait is consistent in mammals and is a defining characteristic of their vertebrate nature.

### Conclusion:
The common trait of mammals from the options provided is that they have **seven cervical vertebrae**.

---