Why does the cage bird in maya angelou's poem sing

The caged bird in Maya Angelou's poem sings to express itself.

Maya Angelou’s poem “Caged Bird” is a symbol of African Americans who are "caged" in their own land by the whites. The symbol of the cage in the poem depicts the restriction of the society. Meanwhile, the caged birds sing the song of liberty and are compared with free birds. So that, the principal theme of “Caged Bird” is freedom.

Angelou's poem employs the metaphor in order to convey the idea that freedom is a natural state and knowledge of this fact cannot be undone by any amount of oppression or imprisonment.

answer; i believe that the   correct answer is (d)the use of descriptive words that bring your reader into the story, not using literal words for check luck