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: Radiology
Best imaging study for the earliest diagnosis of cerebral infarct- 
Select and explain. 
A. FLAIR MRI, B. Non-contrast CT, C. CECT, D. Diffusion-weighted MRI
D: Diffusion-weighted MRI
Answer: D: Diffusion-weighted MRI 
Explanation: Diffusion-weighted MRIDiffusion-weighted MRI detects cytotoxic edema in just a few hours of infarction.