How were 20th century communism and fascism similar?

FULL ANSWERThere is one notable difference between communism and fascism: communism arose as political philosophy with a distinct metaphysics and theory of history; it existed as only an ideology for over half a century before being put into practice. Fascism, on the other hand, arose as a series of policies and political attitudes held by nationalists of various countries during the 20th century.Despite being very different to fascism on paper, communism as a political reality shares many features. Nationalism is key to both ideologies. Members of a country have a firm and unfailing devotion to their homeland, whether it be Germany or Russia. This extreme patriotism justifies the conquest and destruction of ideologically opposed nations

It's most likely choice a, it makes the most sense in my opinion.