The following sentence may have an ERROR in the use of commas. If it does, choose the revision that corrects the error. If it does not have an error, choose "Correct as is." Because they were relieved to have survived the arduous journey along the rugged frontier many settlers were known to kiss the ground upon finally arriving at their destination."

Even though the possible options for revisions were not posted in your question, I believe the best way to correct the sentence is:

Because they were relieved to have survived the arduous journey along the rugged frontier, many settlers were known to kiss the ground upon finally arriving at their destination.

Explanation:

The original sentence did not present a comma between the dependent clause and the independent one. That would have been right if the dependent clause had come after the independent one. That would have been the natural structural order for the sentence. However, that is not the case. The sentence began with the dependent clause - which can be identified by the subordinating conjunction "because". While the normal structure would be "A happened because of B", what we have in this sentence is "because of B, A happened". When we invert the sequence, we should use a comma to separate the clauses. For that reason, the best way to correct the sentence is by adding a comma between the words "frontier" and "many":

Because they were relieved to have survived the arduous journey along the rugged frontier, many settlers were known to kiss the ground upon finally arriving at their destination.

b is the answer for this question.