4.The above-mentioned 56-year-old woman with GBM is maintained on adjuvant temozolomide following concurrent brain radiation therapy and temozolomide. Approximately 4 months after radiation therapy, she presents to the emergency department with complaints of increased shortness of breath and dyspnea on exertion. Her vitals on presentation are as follows: blood pressure 98/58 mmHg, heart rate 118/minute, respiratory rate 24/minute, and O₂ saturation 88% on room air. A chest x-ray obtained demonstrates a diffuse bilateral interstitial infiltrate. What is the most likely causative agent?

A. Streptococcus pneumoniae

B. Mycoplasma pneumoniae

C. Aspergillus fumigatus

D. Pneumocystis jirovecii

E. Pseudomonas aeruginosa