Explanation/Reference:
An IS auditor can expect to find system errors to be detailed in the console log.

The user's digital signature is only protected by a password. Compromise of the password would enable access to the signature. This is the most significant risk. Choice B would require subversion of the public key infrastructure mechanism, which is very difficult and least likely. Choice C would require that the message appear to have come from a different person and therefore the true user's credentials would not be forged. Choice D has the same consequence as choice C.

Explanation
The most effective control over visitor access to highly secured areas is to require visitors to be escorted by authorized personnel. This control ensures that visitors are supervised at all times and do not enter any restricted or sensitive areas without permission. It also allows authorized personnel to verify the identity, purpose, and clearance of the visitors, and to monitor their behavior and activities. Escorting visitors also reduces the risk of tailgating, piggybacking, or unauthorized duplication of access credentials.
Requiring visitors to use biometric authentication, monitoring visitors online by security cameras, and requiring visitors to enter through dead-man doors are all examples of technical controls that can enhance visitor access control, but they are not as effective as escorting visitors. Biometric authentication can provide a high level of identity verification, but it does not prevent visitors from accessing unauthorized areas or compromising security in other ways. Security cameras can provide a record of visitor movements and actions, but they may not deter or detect security breaches in real time. Dead-man doors can prevent unauthorized entry by requiring two-factor authentication, but they do not ensure that visitors are accompanied by authorized personnel.
References:
ISC Best Practices for Facility Access Control1
Visitor Management Best Practices From Top Organizations2
8 Best Practices for Setting Up a Visitor Management System3