<p>Can someone help me understand the rule behind number 2? The correct answer is F (I narrowed it down between F and J).</p>
<p><a href="http://i.imgur.com/gAJZ5IF.png%5B/url%5D">http://i.imgur.com/gAJZ5IF.png</a></p>
<p>The conjunction “but” does not need a comma before it because it is not joining two independent clauses. It is just joining 2 prepositional phrases.</p>