Part of the body having a single pair of bones is

Options

A. Pelvic girdle
B. External ear
C. Wrist
D. Lower jaw.

Explanation

To solve the question regarding which part of the body has a single pair of bones, we can analyze the options provided:

1. **Pelvic Girdle**: The pelvic girdle is made up of a single pair of bones known as the hip bones. These bones are connected at the front by a cartilage called the pubic symphysis and are attached to the sacrum at the back. Each hip bone is composed of three parts: ilium, ischium, and pubis. However, when considering the pelvic girdle as a whole, it is indeed a single pair of bones.

2. **External Ear**: The external ear, specifically the auricle or pinna, consists of several structures, including cartilage and skin, but does not have a single pair of bones.

3. **Wrist**: The wrist is made up of eight small bones known as carpals. Therefore, it does not qualify as having a single pair of bones.

4. **Lower Jaw**: The lower jaw, or mandible, is a single bone, but it is not a pair. It is the strongest and longest bone of the face.

Based on this analysis, the correct answer is:

**Pelvic Girdle** is the part of the body that has a single pair of bones.

### Step-by-Step Solution:
1. **Identify the options**: Look at the provided options: pelvic girdle, external ear, wrist, lower jaw.
2. **Examine each option**:
- **Pelvic Girdle**: Contains a single pair of hip bones.
- **External Ear**: Does not consist of a single pair of bones.
- **Wrist**: Contains eight carpals, not a single pair.
- **Lower Jaw**: Is a single bone (mandible), not a pair.
3. **Determine the correct answer**: The pelvic girdle is the only option that consists of a single pair of bones.