Study of population trends is

Options

A. kalography
B. psychobiology
C. biography
D. demography

Answer

To solve the question "The study of population trends is", we need to analyze the given options one by one to determine which one correctly relates to the study of population.

### Step-by-Step Solution:

1. **Analyze the Options**:
- The options provided are:
- Calligraphy
- Psychobiology
- Biography
- Demography

2. **Evaluate Calligraphy**:
- Calligraphy refers to the art of beautiful handwriting. It does not pertain to the study of population trends.
- **Conclusion**: Calligraphy is not the correct answer.

3. **Evaluate Psychobiology**:
- Psychobiology is the study of the biological basis of behavior. It focuses on how biological processes influence behavior, rather than on population trends.
- **Conclusion**: Psychobiology is not the correct answer.

4. **Evaluate Biography**:
- Biography is the detailed description of a person's life. It focuses on individual life stories and does not relate to population studies.
- **Conclusion**: Biography is not the correct answer.

5. **Evaluate Demography**:
- Demography is the statistical study of populations, including the structure, distribution, and trends in population growth, mortality, and natality. It directly relates to the study of population trends.
- **Conclusion**: Demography is the correct answer.

### Final Answer:
The study of population trends is **Demography**.

---