Which political structure gradually became strong under Bolshevik rule?

Correct answer: One party state

The governing concept is the political centralisation that followed the Bolshevik Revolution. After taking power, the Bolsheviks increasingly limited the activities of rival parties and concentrated authority in their own organisation and state institutions. Over time this produced a one-party political structure, even though the revolution had initially involved broader councils and competing socialist groups. Option A is correct because it describes the growing dominance of a single party. An absolute monarchy would restore rule by a king or tsar, a church state would place religious authorities at the centre, and foreign rule would mean control by another country; none describes Bolshevik consolidation.