This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Basic Concepts and Vascular changes of Acute Inflammation, Subject name: Pathology
A 50-year-old woman is discovered to have metastatic breast cancer. One week after receiving her first dose of chemotherapy, she develops bacterial pneumonia. Which of the following best explains this patient's susceptibility to bacterial infection? 
Select and explain. 
A. Depletion of serum complement, B. Impaired neutrophil respiratory burst, C. Inhibition of clotting factor activation, D. Neutropenia
D: Neutropenia
Answer: D: Neutropenia 
Explanation: The impoance of protection afforded by acute inflammatory cells is emphasized by the frequency and severity of infections in persons with defective phagocytic cells. The most common defect is iatrogenic neutropenia secondary to cancer chemotherapy. Chemotherapy would not be expected to deplete serum levels of complement or alter the respiratory burst within activated neutrophils .