Final answer:
James Madison specifically describes the harm of factionalism causing 'instability, injustice, and confusion' in the government in Federalist No. 10, which historically led to the downfall of popular governments.
Step-by-step explanation:
In the context of Federalist No. 10, written by James Madison, the sentence that specifically describes a harm that factionalism can cause to a government is: B. "The instability, injustice, and confusion introduced into the public councils, have, in truth, been the mortal diseases under which popular governments have everywhere perished; as they continue to be the favorite and fruitful topics from which the adversaries to liberty derive their most specious declamations."
This sentence lays out the consequences of factionalism such as instability, injustice, and confusion, which have historically led to the downfall of popular governments. Madison expresses the concern that adversaries of liberty use these outcomes as the basis for persuasive arguments against democratic governance.