A 12-year-old girl has a history of recurrent bulky stools and abdominal pain since 3 years of age. She has moderate pallor and her weight and height are below the 3rd percentile. Which of the following are the most appropriate investigations to make a specific diagnosis?

Clinical profile of the child given in question makes the diagnosis of malabsorption syndrome associated with chronic diarrhoea. Intestinal biopsy is necessary to differentiate chronic diarrhoea due to different pathophysiologic reasons. Work-up of a child suspected to have chronic diarrhoea and malabsorptions includes the following investigations -Repeated stool examination (especially for giardia), Fecal fat excretion studies, D-xylose test, Intestinal biopsy, Specific tests e.g. sweat chloride for cystic fibrosis, serology for celiac disease, exocrine pancreatic function.