Which of the following statements accurately describes the root of trust model in a public key infrastructure (PKI)?
a. In the root of trust model, the root certificate is issued by a third-party CA, not the organization's own CA.
b. The root of trust model defines how users and different CAs can trust one another, with each issuing itself a root certificate.
c. The root of trust model involves a root certificate that is issued by a user, not a CA.
d. The root of trust model involves multiple root certificates, each issued by a different certificate authority (CA).