Derek Is Working at the Help Desk When He Receives

Multiple Choice

Derek is working at the help desk when he receives a call from a client about an issue with the company's email. The customer is very upset about the email issue. He is complaining about the email service and the IT department in general.  
What should Derek do to defuse the situation?

A) Defend the IT department.
B) Hang up the phone.
C) Call the supervisor and ask for help with the customer.
D) Let the customer vent and then restart the conversation.