What action should be taken if food is left out at room temperature for more than 2 hours?

The appropriate action to take when food has been left out at room temperature for more than 2 hours is to discard it. This is crucial for food safety because bacteria can multiply rapidly at room temperature, especially in the "danger zone" between 40°F and 140°F (4°C to 60°C). If food has been in this temperature range for an extended period, it can become unsafe to eat, even if it is reheated thoroughly or refrigerated afterwards. By discarding the food, you eliminate the risk of foodborne illness that could arise from consuming potentially contaminated items.

The other choices do not effectively mitigate this risk. Immediately refrigerating the food does not eliminate bacteria that may have already developed. Cooking the food thoroughly might kill some bacteria but does not make it safe if harmful toxins have already formed. Serving the food after reheating also does not guarantee safety, as it may still be compromised due to the time it spent at unsafe temperatures. Discarding the food is the safest and most responsible course of action.