Exam C2150-609 topic 1 question 20 discussion

A customer has deployed an IBM Security Access Manager V9.0 solution to protect web applications. After the initial authentication between the client and
WebSEAL, WebSEAL can build a new Basic Authentication header and use the ""b option to provide the authenticated Security Access Manager user name
(client's original identity) together with a predefined static password across the junction to the back-end server.
Which configuration option will accomplish this?