Final answer:
Yaxley's title during the Death Eater control of the Ministry of Magic is B) Head of the Department of Magical Law Enforcement, reflecting the influence and power Voldemort's regime exerted over the wizarding community's legal system.
Step-by-step explanation:
In the series of Harry Potter books by J.K. Rowling, when the Death Eaters take control over the Ministry of Magic, Yaxley is given the title of B) Head of the Department of Magical Law Enforcement.
This position is significant as it is one of the most powerful and influential roles within the ministry, having control over the policing of the wizarding community and the enforcement of magical laws.
Yaxley's appointment to this position represents the consolidation of power by Voldemort and his followers within the Ministry.