Final answer:
The best response is to discreetly monitor the arguing guests and intervene if the situation escalates, ensuring the comfort and safety of all guests at the establishment.
Step-by-step explanation:
When dealing with two guests who begin to argue at an establishment, the best course of action is to keep an eye on the situation and intervene if necessary (Option D). Offering free drinks (Option C) is not advisable as it could exacerbate the situation, especially if alcohol is involved. Asking them to leave immediately (Option A) might be premature if the argument is not disruptive to other guests, while ignoring the situation (Option B) can lead to escalation without your awareness.
Your approach should be to monitor the argument discreetly and be prepared to step in to defuse the situation politely and professionally should it become necessary. Ensuring the safety and comfort of all guests is a priority, so intervening with a calm and respectful demeanor is key when necessary. However, involving security or management should be considered if the disturbance continues or escalates.