subject to vs. subjected to and those vs. they

[sarahfzq]

Struggling with A and C, can anyone help?

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

[RonPurewal]

* This is a GMAT Prep problem. It doesn't belong in this folder.

* Please search the forum; there are existing threads on this problem.
Please read those threads, as your question(s) is/are almost certainly answered in them.
If not, please post your questions in the existing threads. Don't start a new thread.

* If you post, please give specifics of your thought process so far.
What do you already understand about these answer choices?
What, specifically, are the parts of these choices with which you have issues?

Thanks.