The simplest way of going about this is

who/that - always refer to noun preceding it

who - could be uncovered for months, jobs or workers.

Workers - ofcourse

Eliminate A & D

In E - establishment of standards - wordy and awkward, eliminate

In C -comma + to establish - Red flag.

Rule - There are 2 cases in usage of infinitive

1. result - when talking about result, the infinitive can be followed by comma

2. Purpose - when talking about purpose, the infinitive can never be followed by a comma.

Hence B is the only option.

Even B is wordy because to people and to workers

the "to" should not be used twice.

There are still some errors left in each of the options, I'll let others contribute as well.

Agre with PC about the 'who'. Who modifies the word that comes immediately before it and should refer to persons not things. So A and D are ruled out.

In C and E, 'who change jobs that could otherwise be uncovered', seems as if the jobs and not the workers are uncovered of insurance.

In B, the participial phrase 'establishing standards' correctly modifies the subject of the previous clause 'health care bill'. The use of additional 'to' does make this sentence wordier, but the use of 'and' after changing jobs helps in clearing the ambiguity that workers are uncovered of insurance.

The proposed health care bill would increase government regulation of health insurance, establish standards that would guarantee wider access to people with past health problems and to workers changing jobs who otherwise could be uncovered for months.
(A) establish standards that would guarantee wider access to people with past health problems and to workers changing jobs who
(B) establishing standards that would guarantee wider access to people with past health problems and to workers who are changing jobs and
(C) to establish standards that would guarantee wider access to people with past health problems and to workers who change jobs that
(D) for establishing standards that would guarantee wider access for people with past health problems and workers changing jobs who
(E) for the establishment of standards that would guarantee wider access for people with past health problems and workers who are changing jobs that



There is something called superficial parallelism

Now how can government regulate health services ...by establishing...x

For b option..
we are using participle -ing modifier that is modifying the previous action of the clause...regulate....

Regulate health service , establish standards are not two different things.



@@PC
any day a -ing modifier is preferable over infinitive modifier

ronniecoleman wrote: @@PC
any day a -ing modifier is preferable over infinitive modifier

In GMAT, I have found that there is always a specific reason why something is correct.
Therefore, I never go by preference.

Even on GMAT prep after getting to a certain point in verbal, it start to test all the exceptions. Hence, I suggest, find specific reasons why an option is correct and why others are wrong.