What certificate is sent along with the Outbound Message?

Universal Containers (UC) wants its closed Won opportunities to be synced to a Datawarehouse in near real time. UC has implemented Outbound Message to enable near real-time data sync. UC wants to ensure that communication between Salesforce and Target System is secure .

What certificate is sent along with the Outbound Message?
A . The Self-signed Certificates from the Certificate & Key Management menu.
B. The default client Certificate from the Develop–> API menu.
C. The default client Certificate or the Certificate and Key Management menu.
D. The CA-signed Certificate from the Certificateand Key Management Menu.

Answer: B