The following sentence contains a transitional word or phrase:

I jumped back on the curb when I heard the car horn otherwise I would have been hit for sure!
Which revision correctly punctuates the sentence?

I jumped back on the curb when I heard the car horn, otherwise, I would have been hit for sure!

I jumped back on the curb when I heard the car horn, otherwise I would have been hit for sure!

I jumped back on the curb when I heard the car horn; otherwise, I would have been hit for sure!

I jumped back on the curb, when I heard the car horn; otherwise I would have been hit for sure!

I jumped back on the curb when I heard the car horn; otherwise, I would have been hit for sure!