What Certificate is sent along with the Outbound Message?

Universal Containers (UC) wants its closed Won opportunities to be synced to a Data Warehouse 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 CA-Signed Certificate from the Certificate and Key Management menu.
B. The default Client Certificate from the Develop–> API Menu.
C. The default Client Certificate or a Certificate from Certificate and Key Management menu.
D. The Self-Signed Certificates from the Certificate & Key Management menu.

Answer: B