Francisco de Zurbaran and Caravaggio were known for their masterful use of A. idealized human forms. B. perspective. C. chiaroscuro. D. scientific knowledge in their paintings.

I believe the correct answer is C. chiaroscuro.

They are known for their masterful use of chiaroscuro, a technique that uses strong tonal contrasts between light and dark to model three-dimensional forms. Caravaggio made the chiaroscuro dominant stylistic element in his art, and his dramatic use of chiaroscuro came to be known as tenebrism. Zurbaran also used chiaroscuro as dominant technique in which he excelled, which is why he gained the nickname Spanish Caravaggio.