Which artistic advancement is noted in the Kritios Boy sculpture?

The Kritios Boy is significant in the history of sculpture due to its demonstration of contrapposto, a technique that involves the positioning of the human body so that the weight is shifted onto one leg while the other is relaxed. This stance creates a sense of naturalism and movement, showcasing a more realistic representation of the human figure compared to earlier rigid poses seen in Greek art.

Contrapposto emphasizes the dynamic relationship between the body and its environment, allowing for greater expression and a sense of life in the sculpture. As such, the Kritios Boy marks a pivotal moment in the transition toward more lifelike and three-dimensional representations in Greek sculpture. This advancement reflects a broader cultural movement towards realism in art during the Classical period, making it a crucial aspect of the work's historical importance.

The other options do not accurately represent the key advancements in the Kritios Boy. The introduction of color in sculpture was more prominent in earlier works, while the material used in the Kritios Boy is marble, not bronze. Additionally, while the figure does exhibit a level of restraint in facial expression, the absence of facial expressions is not a defining characteristic of this piece, nor is it a celebrated advancement associated with it.