GMAT Sentence Correction (SC) | Re: Though the law will require emissions testing of all diesel

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 gasolinepowered, and will not be subjected to emissions-control standards as stringent as they are for diesel-powered vehicles.

'They are for' is the correct idiom; 'they are of' is incorrect. This is where the strategy starts. Remove B and E for using the wrong idiom.
A. powered, and will not be subjected
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