Final answer:
Without specific context from the text, it isn't possible to accurately describe what Sarah does when Mark and his gang taunt John. In literature, Sarah's character is often seen as compassionate and could possibly intervene or support John.
Step-by-step explanation:
The context of the question is not clear enough to determine Sarah's actions when Mark and his gang begin to taunt John. However, in various literature excerpts where Sarah appears, she often exhibits attributes of compassion, thoughtfulness, and a potential for standing up for what is right. In scenarios dealing with confrontations or emotional distress, Sarah is shown to touch people's lives positively. A typical reaction from a character like Sarah could be to intervene in a non-confrontational way, aiming to defuse the situation, or to support John in facing the taunts. Without specific details from the text the student is referring to, it's impossible to provide a definitive answer.