All mammals (except a few) have .............cervical vertebra.

Explanation

**Step-by-Step Solution:**

1. **Understanding Cervical Vertebrae**: Cervical vertebrae are the bones that make up the neck region of vertebrates. Most mammals have a standard number of cervical vertebrae.

2. **General Rule for Mammals**: It is a general biological rule that most mammals have seven cervical vertebrae. This includes a wide variety of mammals such as humans, giraffes, and rats.

3. **Exceptions to the Rule**: There are exceptions to this rule. The manatee and sloth are notable exceptions.
- The manatee has six cervical vertebrae.
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