What are the main aspects of the complementarity of linkages of economic activities? Try to give examples?

Complementarity refers to the relevant economic activities must exist between the supply and demand for raw materials, labor, technology, capital and other aspects of the relationship, as well as infrastructure *** enjoyment, *** with the treatment of three wastes and the market complementary relationship. It is the result and prerequisite of the uneven spatial distribution of population and natural resources, and the complementarity of conditions constitutes interdependence in economic relations. The size of the spatial interaction is directly proportional to the complementarity. For example, coal mining economic activities for machinery manufacturing economic activities to provide fuel coal, and machinery manufacturing for coal mining economic activities to provide mining tools, equipment, the two extremely complementary.