What modification is necessary on the Salesforce side?

A company exposes a REST web service and wants to establish two-way SSL between Salesforce and the REST web service. A certificate signed by an appropriate certificate authority has been provided to the developer.

What modification is necessary on the Salesforce side? (Choose two.)
A . Create an entry for the certificate in Certificate and Key Management
B . Update the code to use HttpRequest.setClientCertificateName()
C . Configure two-factor authentication with the provided certificate
D . Update the code to use HttpRequest.setHeaderQ to set an Authorization header.

Answer: A,B