"Brennan on the Moor" is structured in this way, so that the longer stanzas can follow the tale of Brennan and give more details to the story. The shorter stanzas act as a chorus, which is usually used to come back to the main idea of a song or poem (in this case, the idea that Brennan is the hero of the poem).
Answer:
21. how are you?
22. where
23. im fine thanks
24plenty of milk
25 you you im
Explanation:
This means that they cover different areas which disagree with each other in order to give a balanced argument, but ultimately reach a point of bias -- which we see as valid as they have covered opposing points.
Tragic hero because the prophecies given to him by the witches influence his plan and intensified his ambition