This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
A patient (pigeon handler) presents with interstitial pneumonitis accompanied by headache, backache, and a dry, hacking cough. A pale, macular rash is also found on the trunk (Horder's spots). Likely organism is: 
Select and explain. 
A. Histoplasma, B. Chlamydiae, C. Mycoplasma, D. Aspergillus
B: Chlamydiae
Answer: B: Chlamydiae 
Explanation: Chlamydiae