Which of the following is a possible sign of unauthorized entry/activity?

The choice indicating blank spaces in the "sign out" column of the visitor log suggests that individuals may be leaving without properly checking out, which could imply unauthorized activity. A well-maintained visitor log serves as a record of who is on the premises, and discrepancies in this log can indicate that someone may have entered or exited without following standard procedures. This lack of proper documentation could be a sign that not all visitors are being accounted for, potentially pointing to unauthorized access.

Having blank spaces can raise concerns about security protocols being followed and can serve as a red flag for security personnel. It's crucial for security practices to ensure that all visitors are tracked appropriately to maintain an accurate understanding of who is on-site, as this contributes to overall safety and security.

While the other options provide valid signs of possible unauthorized activity, they may require additional context or verification to ascertain their relevance as direct signs of unauthorized entry.