Instructions: the Following Sentences Form a Paragraph

Instructions: The following sentences form a paragraph. For each set of choices, select the letter of the answer in which conjunctions or conjunctive adverbs are used correctly and punctuation is correct. Which sentences are correct?

A) Many people take the trail to work every day, for it is easy to get to, relatively flat, and safe. The only problem is that it is longer than the city route.
B) Many people take the trail to work every day, but it is easy to get to, relatively flat, and safe. The only problem is that it is longer than the city route.
C) Many people take the trail to work every day; since, it is easy to get to, relatively flat, and safe. The only problem is that it is longer than the city route.