Final answer:
If the hot TCS food on the self-service bar was originally placed at above 135°F but is now at 120°F after two hours of service, the food worker should discard the food.
Step-by-step explanation:
If the hot TCS food on the self-service bar was originally placed at above 135°F but is now at 120°F after two hours of service, the food worker should discard the food. According to food safety guidelines, perishable foods that remain within the temperature range of 40°F to 140°F for more than two hours should be thrown out as it can lead to rapid bacterial growth and make the food unsafe to eat.