A patient presents with bacterial pneumonia and a productive, blood-tinged sputum. The patient's vital signs are an oral temperature of 102.8 °F, a respiratory rate 28 respirations per minute, an oxygen saturation of 85%, a heart rate of 80 beats per minute, and a blood pressure reading of 125/90. Which of the reported information indicates that the antibiotic therapy is effective?

a) Oxygen saturation of 85%
b) Blood-tinged sputum
c) Respiratory rate of 28 breaths per minute
d) Oral temperature of 102.8 °F