<p>Five years in <em>the writing</em> (A), her new book is <em>both a response</em> (B) to her critics' mistrust <em>with</em> (C) her earlier findings and <em>an elaboration</em> (D) of her original thesis. <em>No error.</em> (E)</p>
<p>Why is C incorrect? I realized it was an idiom error so is there a list of idioms i can learn?</p>
<p>Why can't A be wrong? Because it sounds wrong.</p>
<p>C should be “mistrust of.” This isn’t really an idiom, though - an idiom is a grammatically incorrect phrase you have to memorize in order to know. You can reason this one out. “Mistrust” is an action, and placing the preposition “of” after actions indicates the noun form of that action. For example: “his hatred of John” -> John was hated. “Their mistrust of her findings” -> They did not trust her findings.</p>
<p>If you generally need help with idioms, though, I’d recommend checking out silverturtle’s guide if you haven’t already. There’s a list that can start you off.</p>
<p>There’s nothing incorrect about A. Think of the phrase “x years in the making…” If you’ve heard that before and it doesn’t sound weird to you, it’s because it’s a common idiom that means “in the process of being made.” “Five years in the writing” means the same thing; the author has been writing her book for five years.</p>
<p>^ Yes. Do not rely on your inner year, unless you are confident that your inner ear is actually grammatically sound, lacking errors from colloquialism.</p>