A. The client cannot move from a two-tier to a three-tier employment model after the model has been implemented.

B. The client can move from a two-tier to a three-tier employment model at any point of time, irrespective of the existence of work relationships.

C. The client can have both: a two-tier employment model can remain for its existing employees, and a three-tier employment model can be created to hire new employees within the same legal employer.

D. If no work relationships exist in the enterprise or legal employer, then the client can switch from a two- tier to a three-tier employment model.