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: Pediatrics
A child with complaints of cough. Characteristic inspiratory whoop. Sample for investigation is ? 
Select and explain. 
A. Nasopharyngeal swab, B. Tracheal aspiration, C. Cough plate culture, D. Sputum culture
A: Nasopharyngeal swab
Answer: A: Nasopharyngeal swab 
Explanation: Ans. is 'a' i.e., Nasopharyngeal swab "Culture of nasopharyngeal secretion remains the gold stadard for diagnosis of whooping cough"