In patient with ischemic stroke

In patient with ischemic stroke, iv recombinant tissue plasminogen activator has mainly been found useful during the initial :
A) 3 hrs
B) 6hrs
C) 12 hrs
D) 24 hrs

Technically 4.5 hours is the window period

6 hours ideally , but Some books say 4½ hours !! But mostly everyone agrees with 6hours

6 hour golden period

Actually now there are new variants allowed until 9 hours, but 3 hours is the cutoff until which the available ones are effective on any case. And in certain scenarios it’s efficacy is good until 4 1/2 to 6 hours