Which musical effect is created through the use of rhythm, strong accents, and expanded percussion sections?

The correct choice is Primitivism, which is characterized by the use of rhythm, strong accents, and expanded percussion sections. This style emerged in the early 20th century and drew inspiration from primitive cultures and folk elements. Its music often incorporates rhythmic complexity and a focus on percussive sounds, reflecting a raw and energetic aesthetic. Composers associated with Primitivism, like Igor Stravinsky, emphasized these rhythmic qualities to evoke a sense of primal instinct and intensity, which was groundbreaking at the time.

Other styles listed do not focus on these specific elements to the same extent. Romanticism is typically marked by a focus on emotion and expression, Impressionism emphasizes timbre and color rather than strong rhythmic accents, while Expressionism is concerned with the exploration of intense psychological states through form rather than rhythmic complexity. Thus, the distinctive features of Primitivism make it the most fitting answer in this context.