Final answer:
The best approach for a security guard managing a large crowd is to recognize the potential for danger while closely and carefully monitoring the crowd's behavior, using nonaggressive language and strategies informed by emergent-norm theory.
Step-by-step explanation:
When dealing with a large crowd, the best approach for a security guard is to recognize that all crowds have the potential for danger, and monitor what they are doing very closely and carefully. This option is informed by the emergent-norm theory, which suggests that crowds are able to develop their own definition of the situation. Additionally, different types of crowds exist - casual, conventional, expressive, and acting crowds, each with its own dynamics and potential for peaceful or harmful conduct. In any interaction with a crowd, it is important to use nonaggressive language and maintain a state of alertness to ensure safety and order.