In this sentence from the selection, the phrase “up in arms” is best replaced by the word ___

The best replacement for the phrase “up in arms” in this context is C upset.

“Up in arms” typically means to be angry or unhappy about something. Therefore, “upset” accurately conveys that feeling. The other options do not reflect the intended emotion expressed by this phrase.

If you have more questions or need further clarification, feel free to ask!