Which of the following is a possible sign of forced entry?

Open doors, windows, and gates are possible signs of forced entry because they indicate that unauthorized individuals may have accessed a property without permission or proper entry protocols. When assessing the security of an area, a practitioner should look for any indicators that suggest an opening has been breached, particularly if they are found in places that are typically secured. For instance, a door that is visibly ajar or a window that has been broken can signal that someone has forcibly entered the premises, and this could pose a significant security risk.

The other options, while they may raise some concerns about security, do not directly indicate forced entry. Blank spaces in the visitor log might suggest a lack of proper documentation but do not confirm entry. Missing visitor passes could reflect poor management or unauthorized access but do not specifically indicate that there was any forced action to gain entry. Unattended vehicles on the premises after hours could suggest suspicious activity, but they do not provide clear evidence of forced entry into a building or secured area. Thus, open doors, windows, and gates are the most concrete indicators of potential forced entry.