Frictional unemployment is the unemployment that arises
a. from the average of the unemployment rates over an extended period of time.
b. from workers' imperfect information about available jobs.
c. when wage rigidity creates a persistent gap between labor supply and labor demand.
d. during recessions when the unemployment rate is above the natural rate.

B. from workers' imperfect information about available jobs.

Explanation:

Frictional unemployment occurs when looking for work after leaving, with a voluntary job change, with a temporary loss of seasonal work, and with the first job search by young people. The definition reflects the essence of the phenomenon: the labor market is sloppy, not bringing the number of workers and jobs in instant compliance.

In periods of virtually full employment, namely frictional unemployment accounts for a significant portion of total unemployment. In conditions of high unemployment, the share of frictional unemployment is extremely small, with the exception of those sectors of the economy in which there is a shortage of labor.

answer; no longer than a reasonable period of time;

answer; ethnocentrism;