note: all of the answer choices in the version posted at the top of this thread are wrong; the correct answer has been transcribed incorrectly. a correct transcription of this problem may be found at the following link:
https://www.beatthegmat.com/emmision-laws-t49388.html

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@ kajiabeat,

Is" be subjected to" right in meaning? what's the difference in meaning between this phrase and"be subject to"?

"subjected to" is not correct. that construction is generally used when someone or something is put through some kind of stress, oppression, test, or other ordeal:
customers should not be subjected to this kind of treatment.
this device appears to be well made, but it has not yet been subjected to any sort of stress test.

"subject to" means, basically, "under the jurisdiction of"; it is used to state that someone or something is governed by some rule or law. that is the intended meaning in the sentence in this thread.

any difference in meaning between"standard for" and "standard of"? is the latter one wrong or just inappropirate in this sentence?

"standard for" should be followed by the actual aspect that is being regulated.
e.g., new recruits must meet certain standards for physical fitness.
(in the sentence at hand, this is the intended meaning.)

"standard of" will normally be followed by an explicit statement of the standard itself.
e.g. we adhere to a standard of exceptional customer service.

as usual, there are expressions that serve as exceptions to these generalizations ("standard of living", etc.), but i doubt that those exceptions will be tested. by the way, the best way to get an idea of how idiomatic expressions are used is to google them and read through many examples -- this will provide you with a proper context for the use of these expressions. for instance, just google "standard of" and "standard for" (with the quotes), and read a bunch of hits from page 10, page 20, whatever.

is it straight wrong here to put a comma before "and therefore"?

it's misleading because it creates the impression that "almost all of which are gasoline powered" is a modifier by itself; i.e., it creates the impression that the two parts surrounding that phrase are a single clause, and that only those words constitute the modifier.

saketk wrote:Hi Ron, Thanks for help.. Please let me know whether the usage of 'Subjected to' is correct in this sentence..

"Race car engines are subjected to extreme performance demands."

that version works, provided that you are giving some sort of specific context in which the engines are subjected to these demands (e.g., in nascar races, engines are subjected to extreme performance demands.").
if your message is that the engines may, potentially, be subjected to these demands at some point, then "subject to" is more appropriate.