<prompt> A 10-year-old child presents with history of chronic sinusitis and multiple nasal polypi. He also suffers from recurrent chest infections and malabsorption syndrome. Which one of the following tests would be useful for diagnosis?Total IgE estimationESRLevel of angiotensin converting enzymeSweat chloride  <response>: Presence of chronic sinusitis, multiple nasal polypi and malabsorption point towards cystic fibrosis and therefore sweat chloride test would be useful. 