Hormones are :

Options

A. Internal secretion mostly discharged in the blood by endocrine glands
B. Secretion of exocrine glands
C. Chemical substances secreted into the gut
D. Inorganic catalysts

Answer

### Step-by-Step Solution:

1. **Understanding Hormones**: Hormones are chemical messengers that play a crucial role in regulating various physiological processes in the body. They are produced by endocrine glands and are secreted directly into the bloodstream.

2. **Analyzing the Options**:
- **Option 1**: "Internal secretion mostly discharged in the blood by the endocrine gland."
- This statement is correct. Hormones are indeed secreted by endocrine glands (like the pituitary, thyroid, adrenal glands) into the blood.

- **Option 2**: "Secretion of the exocrine glands."
- This statement is incorrect. Exocrine glands (like sweat glands, salivary glands) secrete substances through ducts, not directly into the bloodstream.

- **Option 3**: "Chemical substances secreted into the gut."
- This statement is also incorrect. While some hormones may affect the gut, they are not specifically secreted into it as a primary function. Hormones are secreted into the bloodstream.

- **Option 4**: "Inorganic catalyst."
- This statement is incorrect. Hormones are organic compounds and not inorganic catalysts. They function as regulators of various biological processes rather than as catalysts.

3. **Conclusion**: Based on the analysis of the options, the correct answer is **Option 1**, as it accurately describes hormones as internal secretions discharged into the blood by endocrine glands.

### Final Answer:
Hormones are internal secretions mostly discharged in the blood by the endocrine gland.

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