Final answer:
The late 1950s unfitted styles that were precursors to the 1960s silhouette are known as A-line fashion, characterized by a free-flowing shape that widens towards the hem to form an 'A' shape.
Step-by-step explanation:
The unfitted styles of the late 1950s that began the 60s silhouette are best known as B) A-line fashion. These styles marked a transition from the fitted, curve-emphasizing clothing of earlier decades to a cleaner, straighter line that would become iconic in the 1960s. The A-line silhouette was characterized by its lack of a defined waistline, which allowed for a free-flowing shape that widened towards the hem, creating an 'A' shape. Unlike the explicitly rebellious flapper fashion of the 1920s that emphasized straight lines to minimize curves, or the latter beatnik and mod styles that also played with fashion norms but in various distinct ways, A-line fashion was more about simplicity and ease of movement.
A-line skirts and dresses were practical yet chic, embodying a sense of youthful nonconformity and freedom while also being wearable for everyday activities. This fashion development foreshadowed the more radical styles of the 1960s, which often signified larger cultural shifts towards freedom, nonconformity, and social change. The clean lines and simplicity of the A-line design set the tone for a decade that would see dramatic transformations in fashion and society at large.