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: Dental
Gingival crevicular fluid is measured using: 
Select and explain. 
A. Whatman's filter paper, B. Ph paper, C. Mylar strip, D. Litmus paper.
A: Whatman's filter paper
Answer: A: Whatman's filter paper 
Explanation: None