Writing Questions! Help!

<ol>
<li>Many scientists (concerned) about the danger of radioactive waste (believe) that nuclear reactors using fusion would be preferable (over) (those) using fission. </li>
</ol>

<p>(over) was the wrong one, why?</p>

<ol>
<li>Best way to change the sentence?
Besides, argued opponents, the real issue is time.</li>
</ol>

<p>I chose to leave it as is, but the right answer was "Change 'argued' to 'argue'". Why?</p>

<p>Thanks!</p>

<p>the error here is “over” because it is an idiom error…</p>

<p>preferable should be followed by “to” instead of “over” in this sentence.</p>

<ol>
<li>Preferable to
Well that answers my question about
prefer to vs. prefer over. Is this from CB?</li>
</ol>

<p>I would personally say that “prefer over” is an alternative for “prefer to” in the English language.</p>

<p>Apparently, CB doesn’t think so. If this problem were to be on an SAT I would take, I would email CB about this.</p>

<p>For 2, can you post the passage and full question? It’s not really clear to me.</p>

<p>@ jeffery, its one of the edit the passage questions.
“Besides, argued opponents, the real issue is time.” is the sentence that we are suppose to edit.</p>

<p>Thanks for the help guys!
Is there somewhere I can find a list of commonly used idioms?
And this is from a past PSAT test</p>

<ol>
<li>Are you sure the answer is supposed to be “argue” instead of “argued”?
It just doesn’t make sense to me… Can you maybe show me the passage? Perhaps it makes sense in context. I really can’t see how “Besides, argue opponents, the real issue is time.” can be a correct sentence.</li>
</ol>