This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Medicine
True about CF- 
Select and explain. 
A. Incidence is 1:2000, B. Positive Sweat test, C. Mutation in CFTR gene, D. May presents as meconium ileus
B: Positive Sweat test
Answer: B: Positive Sweat test 
Explanation: A positive sweat chloride test indicates that it is likely that the infant or person tested has cystic fibrosis (CF). Positive sweat chloride tests are typically repeated for verification. The results may also be confirmed by CF gene mutation panel testing. Ref Harrison20th edition pg 288