Final answer:
The song form that has alternating repetitions of a main theme with contrasting sections is called rondo.
Step-by-step explanation:
The song form that has alternating repetitions of a main theme with two or more contrasting sections is called rondo. In rondo form, the main theme returns multiple times, interspersed with contrasting sections. This creates a lively and dynamic structure in the composition. An example of a rondo form is the third movement of Beethoven's Symphony No. 9, known as the 'Ode to Joy'.
Learn more about Understanding different song forms in music