Explanation

The blank refers to the tone of the chair’s remarks, which offended people accustomed to being addressed in a more collegial and egalitarian manner. Thus, you need a word that means non-collegial or non-egalitarian; a simple word like bossy works well.

Choices (D) and (E) give roughly synonymous meanings, but nothing in the sentence supports the idea that the speech was optimistic. Neither ignominious, which means shameful, nor saturnine, which means gloomy, makes sense in the blank, so eliminate choices (A) and (F).

Both imperious and peremptory can mean bossy, so choices (B) and (C) give you appropriate, equivalent sentences.

Hence options B and C are correct!