Final answer:
A) 1189, Philippopolis.
The German military campaign in the Byzantine Empire began in 1189, and Philippopolis's capture allowed the use of Adrianople as a winter rest stop.
Step-by-step explanation:
The German military campaign in the Byzantine Empire began in 1189, and the capture that enabled them to use Adrianople as a rest stop for winter was the capture of Philippopolis. This event corresponds to option A) 1189, Philippopolis. It is important to note that the campaign was part of the larger conflict known as the Third Crusade, during which European powers sought to reclaim the Holy Land from Muslim control. Adrianople, modern-day Edirne in Turkey, served as a strategic location during these military campaigns.