Final answer:
The guest is exhibiting a Personality change, which is a common sign of intoxication marked by an altered behavior pattern after consuming a substance.
Step-by-step explanation:
The sign of intoxication that the guest is exhibiting is D) Personality change. When someone consumes alcohol or another substance, it can lead to altered behavior, such as becoming unusually loud or aggressive after initially appearing shy. This change in behavior is a common indicator of intoxication. It is important to note that different individuals may exhibit different signs of intoxication, and this is just one of the possible indications.