C

The radiograph demonstrates a large, smooth-walled, spherical, homogeneous opacity occupying the right lung field—findings classically described for an intact pulmonary hydatid cyst. Consolidation usually has ill-defined margins with air-bronchograms, a lung abscess shows a thick-walled cavity with an air-fluid level, and congenital AV malformation appears as a serpiginous vascular mass rather than a uniform round opacity. Pulmonary hydatid cysts are well-circumscribed, round masses on chest X-ray and are a recognized cause of cough and fever in school-aged children living in endemic areas [Erdem, 2003, PMID 12536091; Azeemuddin, 2005, PMID 15678293].