This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
Pulmonary mycetomas on radiographs most commonly show as 
Select and explain. 
A. Air fluid level, B. Lucent crescent, C. Eccentric nodule, D. Rim calcification
B: Lucent crescent
Answer: B: Lucent crescent 
Explanation: The fungal ball produces a tumor-like opacity on X ray,but can be distinguished from a carcinoma by the presence of a crescent of air between the fungal ball and the upper wall of the cavity(Air crescent sign).HRCT is more sensitive. Reference:Davidson's Medicine-22nd edition,page no:698.