Answer:
It engages the audience and forces them to think.
It forms a memorable refrain as in the chorus of a song.
Step-by-step explanation:
In this speech, Sojourner Truth repeats the refrain "and ain't I a woman?" in order to force the audience to think about what she is saying. Truth's argument is that despite being a human, and a woman, she is not treated like other people due to her condition of slave. This phrase engages the audience and forces them to think. However, it also serves as a memorable and rhythmic refrain.