Final answer:
When responding to an angry and sarcastic customer complaint, it is important to show empathy and offer to find a solution.
Step-by-step explanation:
When responding to an angry and sarcastic customer complaint, it is important to choose your words carefully and remain calm. The best option is to show empathy and understanding towards the customer's frustration, so option b) "I understand your frustration; let's find a solution." is the most appropriate response. By acknowledging their feelings and offering to find a solution, you can help defuse the situation and work towards resolving the issue.