adamant, unwavering

Explanation

The clue to the blank is passionately insistent of her assertions, signifying that a similar tone helped her team prevail. Recycle the clue and look for words that mean passionately insistent.

Choices (A), (D), and (F) indicate that she would have an insecure, impaired or unsure tone, and can be eliminated. Choice (C) is incorrect because there is no clue that she had an odd tone. Correct choices (B) and (E) both mean unshakably determined and produce equivalent, appropriate sentences.

Hence options B and E is correct!