Which of the following is not characteristic of the body's capillaries ?

Options

A. Thin-walls
B. Highly branched
C. High blood velocity
D. Large total surface area

Answer

To determine which of the following is not a characteristic of the body's capillaries, let's analyze the characteristics of capillaries step by step.

### Step-by-Step Solution:

1. **Understanding Capillaries**:
- Capillaries are the smallest blood vessels in the body. They connect arterioles (small arteries) and venules (small veins) and are crucial for the exchange of substances between blood and tissues.

2. **Characteristics of Capillaries**:
- **Thin Walls**: Capillaries have walls that are only one cell thick. This thinness facilitates the diffusion of gases, nutrients, and waste products.
- **Highly Branched**: Capillaries are highly branched, which increases the surface area for exchange and allows for efficient distribution of blood to tissues.
- **Great Surface Area**: The extensive branching of capillaries provides a large surface area for exchange processes.
- **Low Blood Velocity**: Blood flows slowly through capillaries, allowing time for the exchange of materials. This is in contrast to arteries, where blood flows at a higher velocity.

3. **Evaluating the Options**:
- **Option 1: Thin Wall**: This is a characteristic of capillaries. (Not the answer)
- **Option 2: Highly Branched**: This is also a characteristic of capillaries. (Not the answer)
- **Option 3: High Blood Velocity**: This is NOT a characteristic of capillaries, as they have low blood velocity to allow for exchange. (This is the correct answer)
- **Option 4: Large Total Surface Area**: This is a characteristic of capillaries due to their extensive branching. (Not the answer)

4. **Conclusion**:
- The option that is NOT a characteristic of the body's capillaries is **Option 3: High Blood Velocity**.

### Final Answer:
**Option 3: High Blood Velocity**