This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Imaging of Interstitial Lung Disease, Subject name: Radiology
A breast cancer patient presents with difficulty on breathing. CXR shows? 
Select and explain. 
A. Canon ball metastasis, B. Pneumothorax, C. Pulmonary artery hypertension, D. Interstitial lung disease
A: Canon ball metastasis
Answer: A: Canon ball metastasis 
Explanation: Ans. (a) Canon ball metastasis.