<p>In Angkor, Cambodia's ancient city, a (clever) designed reservoir, five miles long and one mile wide, (supplied fish) (and) helped farmers (to produce) three corps of rice annually. </p>
<p>I know that the answer is A, it should be cleverly but doesn't "to produce" lack parallelism?</p>
<p>Five years in (the writing), her new book is (both a response) to her critics' mistrust (with) her earlier findings and (an elaboration) of her original thesis. </p>
<p>Is this an idiom error?</p>
<p>Nope, parallelism isn’t an issue here. Unless you have “and helped farmers get fish and to produce three crops of rice”, there’s nothing for it to parallel. </p>
<p>The second one looks fine. I might be wrong, though.</p>
<p>The second sentence should read:</p>
<p>Five years in (the writing), her new book is (both a response) to her critics’ mistrust <a href=“of”>b</a>** her earlier findings and (an elaboration) of her original thesis.</p>
<p>I believe the first sentence is correct because helped should be followed by a “to” infinitive or a bare infinitive…</p>