Final answer:
Sparta was focused on the art of war, rather than literature, painting, or philosophy, making war their primary concern and form of 'art'.
Step-by-step explanation:
The Spartans, unlike other Greek city-states, prioritized military excellence above all other forms of art or intellectual pursuit. While other parts of Greece, such as Athens, were producing influential philosophies and epic literature, Sparta was predominantly concerned with waging and excelling in war. Their society was geared towards creating the perfect warrior, evident in their social structure, education system, and disdain for other forms of art, such as literature and painting. For the Spartans, the only 'art' worth mastering was that of warfare, which ruled out options like literature (A), painting (B), and philosophy (C), making (D) War the correct answer to what form of art Spartans were concerned with.