<ol>
<li>Marathon racing, a challenging test of endurance, (has become) (increasingly) popular (among) amateur athletes in the (last few) years. (No Error)</li>
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<p>Why can't C be wrong, and instead replace among with amongst? Are both interchangeable on the SAT?</p>
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<li>(Crossing and recrossing) the stream, stepping on or over slipper rocks, and (following) a trail (that grew) steeper and steeper, the hikers soon realized (how challenging) their day would be. (No Error)</li>
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<p>I thought C was wrong because (that grew) did not math with the verb forms crossing and recrossing, and following. Why and how is it (no error)</p>
<ol>
<li>The warning in the plays (is) clear: (unless) we restore the integrity (of the family), all traditional values (will disappear). (No Error)</li>
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<p>I chose B because shouldn't (unless) be replaced with until? Why is it (no error)</p>
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<li>The dolls in the collection, (all) (more than) two hundred years old, had been (carefully) carved for children (long since) gone. (No error)</li>
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<p>I thought D was wrong because it just seemed like it made the sentence incomplete. How is it right and thus making the answer (no error)?</p>
<ol>
<li>SAT writing MC never checks the proper use of the participles of a word. IE, whose vs who, among vs amongst.</li>
<li>The “grew” refers to the trail independently of the actions of crossing and recrossing. Therefore, nothing is wrong with the sentence because the “how challenging” refers to the hikers only, in which case it makes perfect sense. </li>
<li>“Until” is completely wrong in context of the sentence. It cant replace “unless”. “Until” makes it so that you are expecting something to happen, but an obstacle blocks it to makes it hard to achieve.“Until I get my score report, I won’t known my SAT score.” Here, you are expecting your SAT scores, they will come eventually, but the obstacle of not having the report yet makes the sentence correct. Unless creates more of a foreboding or warning sentence, which is what this one is. “Unless I ask for my score report, I won’t get it.” This sentence is warning that if I don’t take an action, I won’t receive something or something bad will happen(me not getting my report). In the sat sentence you posted it is warning that if we DO NOT take action, values will be lost. So unless is valid in this case.</li>
<li>“long since gone” is and idiom, ie: a phrase that may take more analysis to determine as grammatically correct, but is commonly accepted as truth in modern English.</li>
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