The growth of the railroads led to the abolition of local times, which was determined by when the sun reached the observer's meridian and differingfrom city to city, and to the establishment of regional times.

(A)which was determined by when the sun reached the observer's meridian and differing
(B)which was determined by when the sun reached the observer's meridian and which differed
(C)which were determined by when the sun reached the observer's meridian and differing
(D)determined by when the sun reached the observer's meridian and differed
(E)determined by when the sun reached the observer's meridian and differing

to me, which refer to the abolition of local time, not local time.

I would go with E.

determined and differing are part of an adjective clause that is modifying 'local times'. It's tricky because they don't look the same, but I think they have the same purpose. They both act as participles (just that differing is active) and therefore they are grammatically correct.

'which' always modifies the noun next to it, in this case, 'local times'. I'll take B. the first 'which' introduce the modifier for 'local time' (determined by when the sun reaches the oberser's meridian) and the second 'which' introduces the modifier for 'meridian' (differed from city to city).

Since 'which' is often used to introduce non-essential modifiers, it also means these modifiers can be removed without any change to the meaning to the sentnece. In this case, the sentence still says the growth of railroads led to the abolition of local times and to the establishment of regional times.

B for me.

Yes - E will "sound" better because Kaplan's OA told you so !

Here is my 2 cents on boring English grammar (which Kaplan will never tell you):

Options with "which" are darn wrong - because "which" refers to local times (plural) and cannot have "was".

Some "psycho" can still argue (as someone did in a previous post by calling himself a "psycho") that "which" refers to "abolition" and not to "local time"; then please be prepare to tell me how abolition can be determined by sun's position.

Now between D & E :

"determined" and "differed/ differing" are both participle modifying noun "local times" and can be used for parallel construction. However, there is a subtle difference:

"local times" are determined by something else which is not under control of "local times"; hence it needs a passive construction - "determined by X"

However, local time can differ by itself so it can have an active construction - "differing city to city" - as presented in E.

E is correct .

Last but not least, congratulations to Mr AK47 for posting the first "correct" SC problem with all 5 answer choices, proper underlining and without any other error. If this is any measure of progress, then you are on right track ... kidding ...
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"Education is what remains when one has forgotten everything he learned in school."

oa is E