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: Microbiology
Ouchterlony procedure is a immunodiffusion by 
Select and explain. 
A. Single diffusion in one dimension, B. Double diffusion in one dimension, C. Single diffusion in two dimensions, D. Double diffusion in two dimensions
D: Double diffusion in two dimensions
Answer: D: Double diffusion in two dimensions 
Explanation: Single diffusion in one dimension - Oudin procedure
Double diffusion in one dimension - Oakley fulthorpe procedure
Single diffusion in two dimensions - Radial immunodiffusion
Double diffusion in two dimensions - Ouchterlony procedure