<p>How do we know which idiom to use, when there are multiple idiomatic phrases?</p>
<p>For example, </p>
<p>different to, than, from
impressed by, with
explanation of, for</p>
<p>Or do we not have to know this, as the SAT will test only if we can differentiate the 'wrong' ones from the 'right' ones? (btw, is 'differentiate from' in this sentence correctly used AND is the underlined part also correct? :P)</p>
<p>The 'explanation' one was tested in this year's PSAT, so what is the consensus on WHY one is used over the other? (is 'used over' correct in this context??)</p>