Each sentence has an adverb clause. which one is not correctly punctuated?
-because i have glued my feet to the asphalt, i am fearless.
-i wore my special hiking boots so that i would not lose my grip.
-i won't leave you alone until you retreat from the edge.
-you are going to fall off the cliff, unless you move back.

The last option is not corredctky punctuated because when you are using an adverd to conjoin two sentences or pharses you need to ask your self if the two phrases can be by themselves and make sense. So the last one would be you are going to fall off a cliff and you move back. The second sentence does not make sense so you do not need a comma there. When trying to figure this out remember that if they can stand alone use a comma if not do not put one in the sentence.

The answer is 2) to show the depth of the colonists’ commitment to independence