Final answer:
Karl Marx was indeed a sociologist who believed that the economy influences social structure, which aligns with his theory of historical materialism that proposes economic class struggle drives societal change.
Step-by-step explanation:
The statement 'Karl Marx was a sociologist who believed that the economy influences the social structure' is true. Marx's theory of historical materialism emphasizes that the economic base, or mode of production, shapes the superstructure, which encompasses society's social and cultural institutions. Marx viewed the history of society as fundamentally a struggle between economic classes, primarily between the bourgeoisie, who control the means of production, and the proletariat, the working class. This class conflict is, according to Marx, the impetus for social change and the eventual transition from capitalism to socialism and finally to communism. Therefore, yes, Karl Marx, as a sociologist and economist, held the view that economic factors are fundamental in determining the structure and development of society.