<h1>9)They made a sound recording originally believed to be the distinctive double-tap sound of the elusive bird(, but) later determined it was likely the echoes from a gunshot.</h1>
<p>Shouldn't it be "but" with no comma? The second part of the sentence is dependent because it has no subject? Right?</p>
<p>This is really hard. I wonder if someone here is smart enough to answer it</p>
<p>[it] and [was].</p>
<p>:o</p>
<p>:)</p>
<p>Weird.</p>
<p>later determined it was likely the echoes from a gunshot.</p>
<p>Doesn’t even sound like a sentence.</p>
<p>But wouldn’t “they” later determine it? So they was the subject?</p>
<p>Commas are almost always optional, but it’s best to include them when a sentence has a natural pause.</p>
<p>Umm. </p>
<p>In the McGraw ACT Book it says this for the explanation.</p>
<p>The best answer is B. A comma is used before
a coordinating conjunction joining independent
clauses in a sentence.</p>
<p>I tried an online grammar correction program, and it agreed as well.</p>
<p>What does it really mean to be an independent sentence?</p>
<p>Independent clauses have a subject and verb. But really, if you are a native English speaker, you should be able to hear commas.</p>
<p>I had to wipe out my inner ear in order to improve my English from 18 to 30.</p>
<p>Oh… that’s unfortunate. Commas would be hell without an inner ear.</p>
<p>This is why you should only use the BB for SAT prep (and the Real ACT book for ACT). I would ignore this ambiguous question so you won’t be confused later.</p>