This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: general microbiology, Subject name: Microbiology
Which of the following is not a tube test? 
Select and explain. 
A. VDRL, B. Kahn test, C. Widal test, D. Paul bunnel test
A: VDRL
Answer: A: VDRL 
Explanation: VDRL: Venerial disease Research Laboratory Test Ref: Ananthanarayana & panikers 9th edition