On the basis of the system previously operating in Hong Kong, the Government of the Hong Kong Special Administrative Region may make provisions for local lawyers and lawyers from outside Hong Kong to work and __________ in the Region.

The correct choice is related to the role and functions that lawyers perform in the legal system of Hong Kong. In this context, local lawyers and those from outside Hong Kong are recognized for their ability to represent clients in legal matters, which aligns with the term "advocate." Advocating involves representing clients in court, advising on legal issues, and engaging in negotiation on their behalf, which is essential for the functioning of the legal system.

While "practice" could also seem relevant, in this context, it generally refers to the more comprehensive scope of legal work, including administration and business activities beyond courtroom representation. "Adjudicate" specifically refers to the role of judges or arbitrators who resolve disputes and is not applicable to lawyers who represent clients. The term "retire" is unrelated to their professional activity in the context of legal practice.

Therefore, "advocate" is the most fitting term, effectively capturing the work that lawyers do in representing clients within the legal framework established in the Hong Kong Special Administrative Region.