The theme is about letting go at one point and following your heart.
Answer: I'm fairly certain that the answer is (B) At length, Una checked her tears, and, trying to put away her grief, arose, and, remounting her humble steed, set out again to seek her knight.
Explanation: I'm not 100% sure, by any means, but I think that she has resolve when she tries to put away her grief and remounted her steed.
Which word is supposed to be underlined?
This exchange shows disagreement over military strategy; it recalls the disagreement between Mark Antony and Octavius in act 4 over Lepidus' suitability for a role in the Second Triumvirate. It also foreshadows the future downfall of Rome as a result of their disagreement and hostility.
I hope that helps.