In the context of this case, which symptom might indicate a more severe underlying condition?

The presence of tonsillar exudates is a significant symptom that might indicate a more severe underlying condition, such as streptococcal pharyngitis or infectious mononucleosis. Tonsillar exudates suggest that there is an active infection occurring in the throat region, and this could be indicative of a more serious bacterial process that may require antibiotic treatment.

While clear lung auscultation typically suggests that there are no immediate respiratory issues, a low-grade fever is often seen in many benign viral infections and does not necessarily point to severity. A rapid respiratory rate might indicate distress or anxiety but can also occur in a variety of situations, even in less severe cases, so it does not specifically signal a serious underlying condition in the same way tonsillar exudates do. Thus, the presence of tonsillar exudates serves as a more concerning symptom that warrants further evaluation for potential complications or serious infections.