According to the sectoral shifts hypothesis:_______.
a. frictional unemployment will cause workers to extend their temporary lay-offs.
b. most unemployed workers will return to their previous job because the firm knows the skills of the worker.
c. there will always be a pool of unemployed workers who experience spells of unemployment because they do not aggressively search for work cyclical unemployment will always exceed frictional unemployment.
d. there will be always be some level of unemployment because the skills of the workers do not match the skill requirements of employers.