clawhammer wrote:

Guys, please explain: why 'exposed' is not required to be followed by 'to' in option E? also, why is it required to have 'that' after 'and' in option D?
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see the following sentences:

The party to which they are biased is given unqualified opinion.

--> The party to which they are biased to is given unqualified opinion.

==> Which one is good? Obviously the the first one. Why? You should not use "to" two times.

When you are saying "to which", you are NOT required to say the second 'to'

Second question:

That after AND is not required in the option D because the correct form is "concluded that X and that Y", where X and Y are independent clauses.

Example:

The committee concluded that they can go to the park and that they are not required to pay fee.

"many of the dioxins that are currently uncontrolled" is NOT an independent clause.

HTH.

In E, to which North Americans are exposed is equivalent to that North Americans are exposed to. Hence in to which North Americans are exposed to, the second to would be redundant.

In D, you have a parallelism - two items connected with and. These items need to be parallel, i.e., both having the same function in the sentence: both verbs, both nouns, both relative clauses (e.g., starting with that), etc. If you look at D, you can't slice it in any way that fulfills the parallelism:

"many of the dioxins that are currently uncontrolled" (noun phrase) AND "North Americans are exposed to" (unfinished clause)
many of the dioxins "that are currently uncontrolled" (relative clause) AND "North Americans are exposed to" (unfinished clause)
many of the dioxins that are "currently uncontrolled" (modifier) AND "North Americans are exposed to" (unfinished clause)

This half-baked clause can't be parallel to anything... The easiest way to fulfill the parallelism, which is forced by the word and, is to add that, creating a relative clause parallelism:

many of the dioxins "that are currently uncontrolled" (relative clause) AND "that North Americans are exposed to" (relative clause)

Thanks a lot for the explanations. I'm clearly getting it now.

To make it easier for me, can I tell myself: whenever I see 'that' before one clause, if I'm checking parallelism, must look for 'that' in the other? - is there any exceptions to this?

Parallelism of relative clauses can sometimes mix various relative pronouns (that, which, who, whose, whom):

I saw the boy "that played soccer" and "to whom the ball belonged".
The girl "that visited our house" and "whose father is the doctor" has a dog.

So I wouldn't necessarily look for another 'that'. To get parallelism right you really have to step up from words and identify the function of sentence parts. So the rule would be more like - if I see a relative clause in a parallelism, I should possibly look for an answer choice that parallels it with another relative clause.

Of course, you can have a relative clause in sentence that parallels something else, e.g.:

The prize was given to "the man who won the raffle" and "his family". (parallelism of nouns)

In this case there is no need for another 'that' or 'who'.