An organization is entering into an agreement with a new business partner to conduct customer mailings. What is the MOST important action that the information security manager needs to perform?

A. A due diligence security review of the business partner's security controls
B. Ensuring that the business partner has an effective business continuity program
C. Ensuring that the third party is contractually obligated to all relevant security requirements
D. Talking to other clients of the business partner to check references for performance