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
Oudin procedure is a immunodiffusion by 
Select and explain. 
A. Single diffusion in one dimension, B. Double diffusions in one dimention, C. Single diffusion in two dimensions, D. Double diffusions in two dimensions.
A: Single diffusion in one dimension
Answer: A: Single diffusion in one dimension 
Explanation: Single diffusion in one dimension (Oudin Procedure).