The document discusses the use of "so" in conversational responses to indicate agreement with a yes/no question. Some examples provided are saying "I think so" to mean "I think that is the case", "I believe so" to agree, and "I hope so" to express hopeful agreement. Negative versions include "I don't think so" to disagree and "I hope not" to express hoping something is not the case. When just guessing, responses like "I guess so" or "I suppose so/not" can be used to indicate uncertainty.