When a human being is cold, the superficial blood vessels :

Options

A. dilate, and the sweat glands are inactive
B. dilate, and the sweat glands are active
C. constrict, and the sweat glands are inactive
D. constrict, and the sweat glands are active

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks what happens to the superficial blood vessels in a human being when the body is exposed to cold temperatures.

2. **Identifying the Response to Cold**: When the body is cold, it needs to conserve heat. One of the physiological responses to cold is vasoconstriction.

3. **Defining Vasoconstriction**: Vasoconstriction is the process where blood vessels narrow (constrict), which reduces blood flow to the surface of the skin. This helps to retain body heat by minimizing heat loss to the environment.

4. **Effects on Blood Pressure**: As the superficial blood vessels constrict, blood pressure in these vessels increases. This is a natural response to maintain core body temperature.

5. **Impact on Sweat Glands**: In cold conditions, sweat glands become inactive. This is because sweating is a mechanism used to cool the body down, and it is not needed when the body is trying to conserve heat.

6. **Evaluating the Options**: The options provided in the question likely include:
- Constrict and sweat glands are inactive.
- Dilate and sweat glands are inactive.
- Dilate and sweat glands are active.
- Constrict and sweat glands are active.

Based on the physiological responses discussed:
- The correct answer is that the superficial blood vessels **constrict** and the sweat glands are **inactive**.

7. **Conclusion**: Therefore, when a human being is cold, the superficial blood vessels constrict, and the sweat glands become inactive.

**Final Answer**: The superficial blood vessels constrict, and the sweat glands are inactive.

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