In all rural settlements, the dominant type of economic activity is primary. Primary economic activities involve the extraction or production of raw materials from the natural environment. This includes activities such as agriculture, mining, fishing, and forestry.

Option 2, secondary economic activities, involve the processing and manufacturing of raw materials into finished products. These activities are typically more prevalent in urban or industrial areas rather than rural settlements.

Option 3, tertiary economic activities, involve providing services to individuals or businesses. These activities include professions like healthcare, education, retail, transportation, and tourism. While some rural settlements may have limited tertiary activities, they are not typically the dominant economic activity.

Option 4, quaternary economic activities, involve the knowledge-based sector, such as research, development, and information technology. These activities are more commonly found in urban areas and are not typically dominant in rural settlements.

Therefore, the correct answer is option 1, primary economic activities.