The following sentence contains an introductory phrase:
Seriously I can lift an extra twenty pounds if I yell when I bench press!
Which revision correctly punctuates the sentence?
Seriously I can lift an extra twenty pounds, if I yell when I bench press!
Seriously, I can lift an extra twenty pounds if I yell when I bench press!
Seriously I can lift an extra twenty pounds, if I yell, when I bench press!
Seriously I can lift an extra twenty pounds if I yell, when I bench press!