Asset allocators create portfolios, often in the form of mutual funds, with theintention to turn in good results in both "bull" and "bear" markets.
(A) with the intention
(B) the intention of which is
(C) intended
(D) and intending
(E) so intended as
Though the answer has been provided/discussed I just wanted to touch upon one thing: how to solve such questions when posed in the actual test.
Firstly immediately recognize that there are modifiers and that is what is going to be tested. Secondly recognize what they modify.
There is "Asset allocators create portfolios" and 2 modifiers:
1. often in the form of mutual funds
2. with the intention to turn in good results
Since 1 is not underlined it doesn't matter but still note that it modifies "portfolios". Let us now focus on 2 (this should take you not more than 20-30 seconds to get to this point on the actual test).
Let us now do a vertical scan:
A -> Keep for now
B -> "intention of which" but we don't know what is it that
which is modifying so knock it off. The moment you get pronouns like which, who, whose, whom etc there is typically a flaw hidden to be unearthed

C -> intended modifies the noun immediately proceeding it - mutual funds or portfolios? Well let's just keep it.
D -> "and intending" - the moment you see "and" you realize its a list problem (i.e. parallel construction) so it should have been something like (which would have still been wrong): Asset Allocators
creating portfolios.........and
intending to......." so this is wrong. At this point the question should pop-up in your head - whose intention is it - asset allocators or portfolios. Again hold on to this thought.
E -> "so intended as to" as per the new version of GMAT is incorrect. To quote from OG 11th edition - "the construction 'so X as to Y' is not a correct idiom"
(SC question #33 - "... so debilitating is it as to become an economic drain"). The problem with this is that like most idiomatic usage questions you either know it or you don't know it

BTW interesting point here - see note below*
So we are left with A and C. This is where it becomes slightly tricky. Shouldn't it be the asset allocators who have "intentions" - how can something like portfolios (an inanimate object) have "intentions"? Well if you had marked A at this point I cannot blame you because the difference is very subtle.
Think about it this way - X gives you a good yield, Y gives good returns on the market, and Z gives you great return on investment. Should I replace X, Y and Z with fund managers, wealth managers and realtors to read Fun Manager gives you a good yield, Wealth Manager gives good returns on the market, and Realtor gives you great return on investment.
OR
Mutual Funds gives give you a good yield, Stock gives good returns on the market, and real estate gives you great return on investment.
The answer is clear. It is Portfolio and NOT the Asset Allocators which give the "good results".
So C wins.
Now let us go back to our question - does "with the intention" modify portfolios or mutual funds. Well the answer is portfolio because 1 modifier cannot modify another modifier. Example:
"Pagalguy, the largest forum in India, has over 1,00,000 registered users". Very clearly India doesn't have 1,00,000 registered users but PG does. So there you have your answer.
For each question if you are able to think through this way then you are on your way to mastering SC

Thanks,
Arun
* Interesting point here is that OG contradicts itself because in the 10th edition you had
"The Emperor Augustus, it appears, commissioned an idealized sculpture portrait, the features of which are so unrealistic as to constitute what one scholar calls an 'artificial face.'" The explanation for the same is given as "Choice A, which uses the clear, concise, and idiomatic construction 'so unrealistic as to constitute,' is best.