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
Ca-wheel appearance on USG is seen in: 
Select and explain. 
A. Hydatid cyst, B. Intussusception, C. Hydatidiform mole, D. All
A: Hydatid cyst
Answer: A: Hydatid cyst 
Explanation: Hydatid cyst REF: Sutton's radiology, 7th edition, volume 1 page 771 Signs of Hydatid cyst: Echinococcus Meniscus/crescent/double arch sign: Floating membrane sign: Spoke wheel/Ca wheel appearance Cumbo sign Water Lilly sign: Camalotte sign: A cyst with an undulating membrane Serpent sign: No calcification in lung