Sentence Correction

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 differing from 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

IMO D.

"Determined by.. " and "Differed ..." are past perfect and they both modify "local times".

Yep, it is D but i still am not clear about the "which" usage. Can you elaborate on that ?

Another example :

The increased popularity and availability of televisions has led to the decline of regional dialects, language variations which originate from diverse ethnic and cultural heritages and perpetuated by geographic isolation.

(A) which originate from diverse ethnic and cultural heritages and perpetuated

(B) that originated from diverse ethnic and cultural heritages and perpetuated

(C) originated from diverse ethnic and cultural heritages and perpetuated

(D) originating from diverse ethnic and cultural heritages and perpetuated

(E) originating from diverse ethnic and cultural heritages and perpetuating

same goes with "who"

The man was always aware, sometimes proudly and sometimes resentfully, that he was a small-town Midwesterner who was thrust into a world that was dominated by wealthier, better-educated, and more polished people than him.

(A) who was thrust into a world that was dominated by wealthier, better-educated, and more polished people than him

(B) who had been thrust into a world that was dominated by more wealthy, educated, and polished people than him

(C) who had been thrust into a world dominated by wealthier, better-educated, and people more polished than he was

(D) thrust into a world dominated by more wealthy, educated, and polished people than him

(E) thrust into a world dominated by wealthier, better-educated, and more polished people than he

I do have the same confusions.. My five cents on this:

Some things which we alreday know:

1. Who is used for referring people
2. Which and That can be used to refer things

which - is usually a relative pronoun that is used in introducing non essential modifiers/clauses

That - is usually used in introducing a Essential modifier/clauses..

Given all this, my problem still persists.. is it not difficult to identify an esstial clause to that of a non essential clause? ( off course not if the non essential is seperated by a comma).. What if it isn't?...

Can some one explain this?

In the example above:

The increased popularity and availability of televisions has led to the decline of regional dialects, language variations which originate from diverse ethnic and cultural heritages and perpetuated by geographic isolation.

(A) which originate from diverse ethnic and cultural heritages and perpetuated

(B) that originated from diverse ethnic and cultural heritages and perpetuated

(C) originated from diverse ethnic and cultural heritages and perpetuated

(D) originating from diverse ethnic and cultural heritages and perpetuated

(E) originating from diverse ethnic and cultural heritages and perpetuating

As MGMAT says it is preferable to introduce a modifier using a Relative pronoun and a simple verb form than using the ing VERB form..According to this D&E should be ruled out..

The options narrow down to A,B, and C...
Now the choice lies between essential and non essential
If "diverse ethnic and cultural heritages" are essential then B is the choice..If it is non essential then C is the answer...

What is the OA?

The increased popularity and availability of televisions has led to the decline of regional dialects, language variations which originate from diverse ethnic and cultural heritages and perpetuated by geographic isolation.

C,D,E are ruled out because it need "that or which ".
Which needs a comma, to elaborate the things...
So, A is ruled out.

IMO B.
What is the OA?

The man was always aware, sometimes proudly and sometimes resentfully, that he was a small-town Midwesterner who was thrust into a world that was dominated by wealthier, better-educated, and more polished people than him.

small town westerner thrust into the world.. creates a run on.. so rule out D & E.

NOW, the key is "Who was Thrust" or Who had been thrust"...
With the complete sentence.. it has to be had been thrust...
So A is ruled out.
between B & C, more wealthy is redundant to wealthier ...
So IMO It has to be C..
what is the OA

Ajeet Gupta wrote:The increased popularity and availability of televisions has led to the decline of regional dialects, language variations which originate from diverse ethnic and cultural heritages and perpetuated by geographic isolation.

C,D,E are ruled out because it need "that or which ".
Which needs a comma, to elaborate the things...
So, A is ruled out.

IMO B.
What is the OA?

Although GMAT prep materials say which will usually be followed by a Comma, there is no hard and fast rule for a comma being there..
"Which" does not neccessarily need a comma, preferably there should be or there will usually be a comma. But not always..Correct me if i am wrong..

IT IS A GOOD QUESTION