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?
The Outbound Message uses the default Client Certificate or a Certificate from Certificate and Key Management menu to ensure secure communication between Salesforce and the Target System. This option provides the most comprehensive flexibility and matches the typical configurations required for secure certificates in Salesforce integrations.
https://developer.salesforce.com/docs/atlas.en-us.api.meta/api/sforce_api_om_outboundmessaging_setting_up.htm "On the Certificate and Key Management page, in the API Client Certificate section, click the API Client Certificate."
Agreed - should be "D"
D it is as outlined in other comments and links