The regulation by an organism of chemical composition of its blood and body fluids and other aspects of its internal environment so that physiological processes can proceed at optimum rates is called

Options

A. a) metabolism
B. b) enthalpy
C. c) entropy
D. d) homeostasis.

Explanation

To answer the question regarding the regulation of an organism's internal environment, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the regulation of the chemical composition of blood and body fluids, as well as the maintenance of an internal environment that allows physiological processes to function optimally.

2. **Identifying Key Terms**: The key terms in the question are "regulation," "chemical composition," "blood," "body fluids," "internal environment," and "physiological processes."

3. **Defining Homeostasis**: The process that maintains a stable internal environment in response to changes in the external environment is known as homeostasis. It involves various physiological mechanisms that regulate factors such as temperature, pH, and concentrations of ions and nutrients.

4. **Evaluating Options**:
- **Option A: Metabolism** - This refers to all biochemical reactions occurring within a cell, not specifically the regulation of the internal environment.
- **Option B: Enthalpy** - This term relates to heat or energy within chemical bonds, which does not pertain to the regulation of internal conditions.
- **Option C: Entropy** - This describes the degree of disorder in a system, which is not directly related to maintaining a stable internal environment.
- **Option D: Homeostasis** - This is the correct term that describes the regulation of the internal environment to maintain stability and optimal functioning of physiological processes.

5. **Conclusion**: Therefore, the correct answer to the question is **homeostasis**.

### Final Answer:
The regulation by an organism of chemical composition of its blood and body fluids and other aspects of its internal environment so that physiological processes can proceed at optimum rates is called **homeostasis**.

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