Which of the following would be a red flag for potential pest issues?

The presence of droppings or frass is a significant indicator of pest activity and serves as a crucial red flag for potential infestations. Droppings, which can vary in size and shape depending on the pest involved, indicate that pests such as rodents or insects have been frequenting the area. Frass, a term used to describe the feces of wood-boring insects like termites or carpenter ants, also signals that these pests are present. Noticing these signs can lead to prompt action for pest control, making it vital to be aware of such indicators in any pest management scenario. Addressing these signs quickly can help prevent further damage or health concerns associated with pest infestations.

While other options presented may suggest a lack of pest issues, they do not directly indicate any pest presence and therefore do not serve as red flags. For instance, sealed windows and dry, polished wood surfaces could suggest that an area is maintained well and managed to prevent pest entry, while uncluttered spaces can lead to easier identification of potential infestations but don't necessarily indicate a problem in themselves.