Which of the following is a sign of heavy drinking?

Frequent blackouts or memory loss is a significant sign of heavy drinking because it indicates a level of alcohol consumption that impairs brain function. When someone drinks heavily, their ability to form new memories can be compromised, resulting in gaps in their recall of events during intoxication. This is often due to the way alcohol affects the hippocampus, the area of the brain responsible for memory formation. Persistent memory loss can indicate chronic alcohol use, which can have serious consequences for a person's health, safety, and social relationships.

In contrast, drinking in moderation is associated with responsible behavior, while feeling relaxed after a drink is a common effect of alcohol that does not necessarily indicate heavy consumption. Enjoying social events can imply moderate or even responsible drinking, as many people participate in social gatherings without drinking to excess. Therefore, frequent blackouts or memory loss stands out as a clear warning sign of problematic drinking behavior.