The CEO for company A has asked the security engineer to design a PKI for company A. The CEO has asked that it allow company A users to send signed and
encrypted emails to company B. The users from company B must have an inherent trust in certificates from company A, because the security policy of company B
disallows adding of new CAs to their trusted root container. Which of the following is the BEST solution?

A.
Request email certificates for the users of company A from the PKI of company B.

B.
Build a new CA within the boundary of company A and issue email certificates to the users

C.
Establish a sub CA of company B’s root CA to issue email certificates to the users.

D.
Procure the services of a common Internet root CA to issue email certificates to the users.