Sentence Correction

Though the law will require emissions testing of all diesel vehicles, from tractor
trailers to excursion buses, it will have no effect on sport utility vehicles, almost all of
which are gasoline powered, and will not be subjected to emissions-control standards
as stringent as they are for diesel-powered vehicles.
A. powered, and will not be subjected to emissions-control standards as stringent as they
are for
B. powered, and therefore not subjected to emissions-control standards that are as
stringent as those of
C. powered and therefore not subject to emissions-control standards as stringent as those
for
D. powered, which are not subject to emissions-control standards as stringent as they are
for
E. powered and therefore they are not subject to emissions-control standards as stringent
as those of

A- law will not be subjected to - wrong, Sports utility vehicles will not be subjected to is required
B-same as A
C- Is the construction. But law will have no effect on ..... sports utility vehicles, Almost all of which are gasoline powered and therefore not subject to..
what is subject of 'and therefore not subject to..' in C- is it sports utility vehicles ?
D- need those
E- --Modifier and complete sentence - not parallell

'almost all of which are gasoline powered (Modifier)
and therefore they are not subject to emissions-control standards as stringent as those of'

C- almost all of which are gasoline powered and therefore not subject to emissions-control standards as stringent as those for
-- sport utility vehicles not subject to emissions-control standards as stringent as those for
Does it mean under the jurisdiction sport utility vehicles are not subject to emissions-control standards
D- almost all of which are gasoline powered, which are not subject to emissions-control standards as stringent as they are for
-- which in 2nd part refers to which in first part? (that is almost all of Sports unitility vehicles)
OR what does 'which' in 2nd part refer to ??
Secondly, what is wrong with usage of 'they' in Option D. I understand 'those' is commonly used during comparison but could not make out whats worng with 'they'. Is it because they refers to subject (which) in previous sentence which is sport unitility vehicles

Thanks for the invite to chime in here! This one's pretty interesting and takes a little time to really dig in. The two big problems with D:

-That second "which" is in some really strange placement - it's trying to be parallel to "almost all of which" but I don't think it pulls it off. There isn't a good noun right before the word "which" and even if you then drop out the previous "which" modifier ("almost all of which...") you're breaking up parallel structure in an awkward way. If that's my only decision point between C and D it's enough to make me strongly lean C, but then there's also:

-"they" in D, and you ask a great question about that. "They" really has to mean "the same they". So you could say "the company directors met for breakfast, and over breakfast they decided to...". "They" clearly means those same directors. What's tricky here is that "they" can't refer to the same emissions control standards for SUVs because the whole point of the sentence is to show that the two sets of emissions-control standards are different.

There's a little more nuance to it than just that - you could say "strawberries grow larger in California than they do in Oregon" but mainly because you're talking about "general strawberries" first. But you can't say "California strawberries grow faster than they do in Oregon" because "they" can't refer to California strawberries there. So there's some subtlety in there but essentially if you suspect that "they" might be referring to a slightly different noun than it should (as it is here) it's a good place to investigate further and look for an answer that clearly corrects the potential problem.

I think I will go with option C.

The subject of 'and therefore not subject to..' is Sportc utility vehicles , because of the use of 'subject'. Generally "someone subjected me to something" is the usage of 'subjected' hence the use of just 'subject' suggests that SUV is the subject of the sentence.

moreover C because I also thought the correct sentence should have 'for' in the end.. i.e 'standards
as stringent as they are for'

so that leaves us with option A,C and D. A and D are wrong for the reasons you mentioned. Is my logic correct?

amnesty17 wrote: C- almost all of which are gasoline powered and therefore not subject to emissions-control standards as stringent as those for
-- sport utility vehicles not subject to emissions-control standards as stringent as those for
Does it mean under the jurisdiction sport utility vehicles are not subject to emissions-control standards

From the sentence actually SUVs will also be subjected to emissions-control standards, but those emissions-control standards will not be as stringent as emissions-control standards for diesel-powered vehicles.

amnesty17 wrote: D- almost all of which are gasoline powered, which are not subject to emissions-control standards as stringent as they are for
-- which in 2nd part refers to which in first part? (that is almost all of Sports utility vehicles)
OR what does 'which' in 2nd part refer to ??

which as it is currently used is way far from SUVs. An interesting thing to note however, is that an extra and in D could have made all the difference:

...sport utility vehicles, and almost all of which are gasoline powered, which are not subject to emissions-control standards..

The problem with they still remains though. There is another issue with D by the way. This is more from a meaning perspective. because SUVs are gasoline powered, they are not subjected to stringent emissions-control standards. This cause and effect is not coming out in D at all, for it seems to suggest two disparate facts about SUVs:

a. They are gasoline powered
b. They are not subject to emissions-control standards as stringent