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: Radiology
"Signet ring appearance” on CT is seen in 
Select and explain. 
A. Bronchitis, B. Emplysema, C. Bronchiectasis, D. Bronchogenic Carcinoma
C: Bronchiectasis
Answer: C: Bronchiectasis 
Explanation: Bronchiectasis may result from an infection or medical condition, such as pneumonia or cystic fibrosis. Mucus builds up and breeds bacteria, causing frequent infections.
Symptoms include a daily cough that occurs over months or years and daily production of large amounts of phlegm.
Treatment may include physiotherapy and medication, such as antibiotics and drugs to help loosen mucus.