D. She gives Brigid a letter addressed to Marsden's wife that would expose Marsden.
Explanation:
Page 172, "...I've written a letter to Mr. Marsden. I told him if he dismissed you or bothered you in anyway I would tell his wife exactly what happened in the weaving room. Now here is the letter addressed to her..."
The suffixes -ible and -able mean that it is able to be done. For example, edible means that it can be eaten; drivable means it can be driven; disposable means it can be disposed of.
