<p>Second question: Parsing a bit of the syntax is always a good way to solve questions that may involve faulty parallelism. But there’s somewhat of a complicating matter here: “whether” functions a bit loosely when it comes to syntax. In contrast to the easy rule that we can apply to correlative conjunctions (“either…or”, “neither…nor”, etc.), the two objects separated by “or” or “nor” that follow “whether” do not have to entirely agree. </p>
<p>Here’s how we would analyze parallelism for correlative conjunctions:</p>
<p>I want neither [to walk] nor [run]. should be</p>
<p>I want neither [to walk] nor [to run]. or I want to neither [walk] nor [run]. (In the latter sentence, “to” carries to both objects by appearing before “neither.”)</p>
<p>Strict and easy: Both objects must be perfectly parallel.</p>
<p>But here’s the liberal stuff we can do with “whether”:</p>
<p>I don’t know whether [he’s ready] or [not]. (The “or not” phrase is a quick way to avoid crafting a parallel phrase, such as “he’s not ready.”)</p>
<p>I don’t know whether he’s ready. (In fact, we can accept “or not” as implicit and excise it utterly.)</p>
<p>I don’t know whether [he’s ready] or [not ready]. (The subject effectively carries to both objects.)</p>
<p>We can’t do anything, though. For example, gerund-gerund and infinitive-infinitive agreement is one flavor of parallelism that cannot escape the tenuous grasp of “whether”:</p>
<p>We can’t decide whether running or to walk is the better idea. should be</p>
<p>We can’t decide whether to run or to walk is the better idea. or We can’t decide whether running or walking is the better idea. </p>
<p>But we do have the freedom to rephrase the first correction as</p>
<p>We can’t decide whether to run or walk is the better idea.</p>
<p>So the problem with the question you provide isn’t really a lack of parallelism. The answer is simply that “are” and “they” are reversed. Currently, the predication is interrogative: Are they done? Let’s make it declarative: “they are.” Rewrite:</p>
<p>The question of whether certain chemical fertilizers are a curse or they are a blessing is still being debated.</p>
<p>It could also be:</p>
<p>The of whether certain chemical fertilizers are a curse or a blessing is still being debated.</p>
<p>Hope these help.</p>