Why does unemployment arise and what makes some unemployment unavoidable?

What will be an ideal response?

In a dynamic economy some unemployment is unavoidable. For instance, growth means that some workers will always be entering the labor force without a job and therefore be unemployed. Consumers changing their demand for one good over another means workers in the newly less-favored industry will lose their jobs and also be unemployed. Moreover some workers will always be leaving their current job to search for a better job and these workers, too, will be unemployed. So some unemployment is unavoidable as the economy churns and reacts to changes.