i) When we exploit natural resources, it is an activity of the primary sector. eg., agriculture, mining, forestry.
ii) The natural resources are changed into other forms through the process of manufacturing, i.re. manufacturing sector uses natural products as its raw materials.
iii) All services that enable us to pursue primary and secondary activities are listed as tertiary activities. For example, transport, education, medical facilities.
iv) Primary and secondary activities cannot produce a good unless they are aided by the tertiary sector.
v) Service sector does not produce a good. For example, the internet cafe, ATM booth, call centres are the services required for manufacturing industries etc. Railways, roads are needed to assist agricultural production.