User from two organizations, each with its own PKI, need to begin working together on a joint project. Which of the following would allow the users of the separate PKIs to work together without…

A trust model, specifically cross-certification or a bridge CA arrangement, enables two independent PKIs to mutually recognize each other's Certificate Authorities. By establishing this trust relationship, certificates issued by either organization's CA are considered valid by the other, allowing users to authenticate and communicate without certificate trust errors.

Stapling (OCSP stapling) is a performance and privacy optimization that allows a web server to cache and present its own certificate revocation status, which does not address cross-organizational PKI trust issues.

An Intermediate CA is a subordinate CA within a single PKI hierarchy used to delegate certificate issuance, but it does not by itself establish trust between two completely separate PKI infrastructures.

Key escrow is a mechanism for storing copies of cryptographic keys with a trusted third party for recovery purposes, and has no role in establishing trust between two separate PKIs.