The correct answer is option C: C, A, D, B.

- Regional analysis: This approach emerged in the early 20th century and focused on the systematic study of regions. It aimed to understand the characteristics and patterns of different regions, including their physical, cultural, and economic aspects. Researchers analyzed the spatial distribution of various phenomena and identified regional variations. This approach laid the foundation for the study of geography as a discipline.

- Areal differentiation: Areal differentiation is a concept that emerged in the mid-20th century. It refers to the process of identifying and understanding the differences and similarities between different areas or regions. This approach aimed to explain the spatial variations in physical and cultural phenomena and to classify regions based on their distinct characteristics. Researchers used various methods, such as mapping and statistical analysis, to analyze and compare different areas.

- Behavioural school: The behavioural school of geography developed in the 1960s and 1970s. It focused on the study of human behavior in relation to the environment. This approach emphasized the importance of understanding how individuals and groups interact with their surroundings and how their actions shape the landscape. Researchers used techniques such as surveys and interviews to gather data on human behavior and analyzed it to gain insights into spatial patterns.

- Postmodernism: Postmodernism is a relatively recent approach in geography that emerged in the late 20th century. It challenges the traditional notions of objectivity and truth in geographical research and emphasizes the subjective nature of knowledge and the importance of multiple perspectives. Postmodern geographers question the idea of a single, stable reality and highlight the role of power and discourse in shaping our understanding of space and place. They explore issues such as identity, representation, and the construction of meaning in geographical research.

In chronological order, the development of these approaches would be: C, A, D, B. Regional analysis emerged first, followed by areal differentiation, then the behavioural school, and finally, postmodernism.