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: Medicine
In a patient with ischaemic stroke, intravenous recombinant tissue plasminogenactivator has mainly been found to be useful during the initial - 
Select and explain. 
A. 3 hours, B. 6 hours, C. 12 hours, D. 24 hours
A: 3 hours
Answer: A: 3 hours 
Explanation: None