This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: parasitology, Subject name: Microbiology
[{'content': 'A definitive diagnosis of ascariasis can be made by observing which of the following \nSelect and explain. \nA. An adult worm passed during a bowel movement, B. Larvae in x-ray of lungs, C. Motile larvae in a stool sample, D. An eosinophilia in a differential white blood cell count', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Identification of adult worms passed by an individual can ensure a definitive diagnosis. Although an eosinophilia accompanies ascariasis, this condition can be caused by other infections and by various allergic conditions. Motile larvae in a stool are indicative of infection with Strongyloides stercoralis. Nematode larvae cannot be seen in an x-ray.', 'role': 'assistant'}]