Explanation:

- Option 1: a dichotomy

- This means dividing settlements sharply into two groups: rural and urban, with no overlap or transition between them.

- Option 2: a continuum

- This means there is a gradual transition from rural to urban areas, forming a spectrum rather than two distinct categories. Many settlements fall somewhere in between pure rural and pure urban.

- Option 3: a dialectical system

- This means rural and urban settlements interact and influence each other in a dynamic way, but it isn't the standard way used to describe spatial distribution.

- Option 4: urban development

- This refers to the growth and expansion of urban areas. It is a process, not a way to categorize rural and urban distribution.