Final answer:
Kaiser Wilhelm II rationalizes Germany's participation in the Boer War as a defense of Germanic territories and a duty to support German relatives and kin, regardless of location.
Step-by-step explanation:
The statement that best summarizes Wilhelm's rationalization of the German Empire's participation in the Boer War against the United Kingdom is D) Nationalism's disregard for imperial borders demanded Germany defend the territory of foreign Germanic nennles.
In the passage, Kaiser Wilhelm II declares his complete dedication to peace on the continent of Europe and downplays the significance of the Boer War in Africa. He emphasizes the importance of supporting German relatives and kin, regardless of where they live. This statement suggests that Wilhelm believes Germany has a duty to defend German territories overseas, even if it means disregarding imperial borders.