Final answer:
The first fully integrated musical with a 15-minute dream ballet reflecting Laurey's struggle to choose between two men is Oklahoma! by Rodgers and Hammerstein.
Step-by-step explanation:
The first fully integrated musical that includes a 15-minute dream ballet reflecting Laurey's struggle to choose between two men is Oklahoma! by Rodgers and Hammerstein. This 1940's musical was a groundbreaking production that combined social issues with dramatic dance sequences, musical scenes, love triangles, and a full-fledged psychological dream ballet. Agnes de Mille's choreography vividly depicted Laurey's desires and struggles, and the music was composed to fit the choreography, setting a new standard for musical theater.