How Are Cost-Of-Living Differentials Handled by Employers When Employees Are

How are cost-of-living differentials handled by employers when employees are transferred from one location to one with a higher cost of living?

A) payment of a nonrecurring, lump sum amount
B) raise employee's base salary
C) pay an ongoing differential for ongoing costs plus a lump sum amount
D) payment of a differential for ongoing costs
E) all of the above