The correct answer is C. His ability to communicate with the public.
Step-by-step explanation
Adolf Hitler was a German politician known for being the leader of the National Socialist Workers Party and leading Germany and Europe to World War II for his expansionist interests and fascist and nationalist ideals. According to the description made by the British embassy in 1937, his political success was due to his effectiveness in speaking in public when the author mentions that "As a speaker, Hitler exercises amazing dominance over a German audience, presumably because public speaking is an art unknown in Germany ", highlighting that his leadership and his way of communicating to the public was a unique feature in Germany at this time. The author also emphasizes when saying that "he has measured the German audience during his fifteen years of apprenticeship with amazing precision", allowing to glimpse Hitler's extensive knowledge of the public he is addressing and who knows how to manipulate his thinking what It led to high support and his political success. Therefore, the correct answer is C. your ability to communicate with the public