My 2 cents..
Researchers have questioned the use of costly and experimental diagnostic tests to identify food allergies, such as
milk, that supposedly disrupt normal behavior.
(A) to identify food allergies, such as-> word following such as points back to allergies thus eliminate it(milk is not an allergy)
(B) to identify food allergies, like -> again milk is not allergy,
(C) to identify food allergies, such as to-> means allergies because of milk, sounds good
(D) for identifying food allergies, like that of-> sounds awkward, eliminate it
(E) for identifying food allergies, such as "for"-> awkward usage.eliminate it
1) So much so that....
2) So as to.....
3) Such as to.....
If it is true that this list of 3 different constructions are always wrong,
-> no I don't think so, if you have easier and correct options, we should go for them as these are wordy
then what am I missing here and why do we have an exception in this problem?