This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetics, Subject name: Medicine
Most sensitive investigation for cystic fibrosis is? 
Select and explain. 
A. CT scan, B. Ultrasound, C. Sweat electrolytes, D. Tomogram
C: Sweat electrolytes
Answer: C: Sweat electrolytes 
Explanation: Ans. (c) Sweat electrolytesRef: Harrison's Medicine 18th ed p 2149-50