Which of the following substance acts as stimulator ?

Options

A. Vitamin
B. Enzyme
C. Hormone
D. Carbohydrate

Answer

To solve the question "Which of the following substances acts as a stimulator?" we will analyze each of the given options: vitamins, enzymes, hormones, and carbohydrates.

### Step-by-Step Solution:

1. **Understanding the Options**:
- **Vitamins**: These are organic compounds that are essential for normal growth and nutrition. They are required in small quantities in the diet because they cannot be synthesized by the body. However, vitamins do not directly stimulate physiological processes.

- **Enzymes**: Enzymes are biological catalysts that speed up chemical reactions in the body. While they play a crucial role in metabolic processes, they do not act as stimulators in the sense of triggering physiological responses.

- **Hormones**: Hormones are chemical messengers secreted by endocrine glands into the bloodstream. They regulate various physiological processes and can stimulate specific activities in target organs or tissues. For example, insulin stimulates glucose uptake in cells, thus playing a critical role in metabolism.

- **Carbohydrates**: Carbohydrates are macronutrients that provide energy to the body. While they are essential for energy production, they do not act as stimulators in the same way hormones do.

2. **Identifying the Correct Answer**:
- Among the options, hormones are the only substances that act as stimulators. They are responsible for initiating and regulating various physiological activities in the body.

3. **Conclusion**:
- The substance that acts as a stimulator is **hormones**.

### Final Answer:
The correct option is **hormones**.

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