Which of the following statements is true of the contingent workforce of an organization?

a$.$

It includes employees who work more than $50$ hours a week.

b$.$

It includes all part$-$time employees who are employed by the organization to fill in for permanent employees during peak demand.

c$.$

It refers to the permanent employees of an organization.

d$.$

It refers to the employees who feel guilty over keeping their jobs when others are laid off as part of the rightsizing process of the organization.