Sentence Correction

Unlike the steam locomotive, which required an hour or two of firing up before it was possible to move under its own power, nearly full power could be summoned almost instantly from the cold engine of a diesel locomotive.

(A) it was possible to move under its own power, nearly full power could be summoned almost instantly from the cold engine of a diesel locomotive
(B) it was possible to move under its own power, the diesel locomotive's engine, when cold, could produce nearly full power almost instantly
(C) it could move under its own power, the diesel locomotive could summon nearly full power from a cold engine almost instantly
(D) moving under its own power, the cold engine of the diesel locomotive could produce nearly full power almost instantly
(E) moving under its own power, almost instantly a diesel locomotive could summon nearly full power from a cold engine

Ron said once for this SC
the original comparison starts with "Unlike the steam locomotive, ...", followed by a modifier. you can kill this modifier in your consideration of the basic structure of the sentence, as modifiers don't count as part of basic structure.
the next part is the main clause. because the comparison is to the steam locomotive, you MUST start the main clause with "the diesel locomotive". you shouldn't precede that with anything - such as the adverb (almost instantly) in choice (e). in order for the comparison to be clear, you MUST begin the main clause with the item that provides the other half of the comparison.

understand. but I have another problem, -->focus on meaning CE ,
like "almost instantly a diesel locomotive could summon nearly full power from a cold engine" is different from the "the diesel locomotive could summon nearly full power from a cold engine almost instantly"
does some differences exists in meaning about C and E here?

because the comparison is to the steam locomotive, you MUST start the main clause with "the diesel locomotive". you shouldn't precede that with anything - such as the adverb (almost instantly) in choice (e)

does some differences exists in meaning about C and E here?

- Dude, When it has been said that the comparison is not apt, why bother about the meaning.

Yes, the difference is that if "almost instantly" is used in the beginning, it seems that the locomotive is trying to summon full power from a "cold engine". It tends to change the original meaning.

crack30 wrote:does some differences exists in meaning about C and E here?

Well if you pay close attention, you will notice that there no comma after "almost instantly" in option 'E'.
It may mean that "almost instantly" modifies only the noun "a diesel locomotive"
However, "almost instantly" is intended to modify the verb "could summon" or second clause i.e. "a diesel locomotive could summon nearly full power from a cold engine"

crack30 wrote:Unlike the steam locomotive, which required an hour or two of firing up before it was possible to move under its own power, nearly full power could be summoned almost instantly from the cold engine of a diesel locomotive.

(A) it was possible to move under its own power, nearly full power could be summoned almost instantly from the cold engine of a diesel locomotive
(B) it was possible to move under its own power, the diesel locomotive's engine, when cold, could produce nearly full power almost instantly
(C) it could move under its own power, the diesel locomotive could summon nearly full power from a cold engine almost instantly
(D) moving under its own power, the cold engine of the diesel locomotive could produce nearly full power almost instantly
(E) moving under its own power, almost instantly a diesel locomotive could summon nearly full power from a cold engine

Ron said once for this SC
the original comparison starts with "Unlike the steam locomotive, ...", followed by a modifier. you can kill this modifier in your consideration of the basic structure of the sentence, as modifiers don't count as part of basic structure.
the next part is the main clause. because the comparison is to the steam locomotive, you MUST start the main clause with "the diesel locomotive". you shouldn't precede that with anything - such as the adverb (almost instantly) in choice (e). in order for the comparison to be clear, you MUST begin the main clause with the item that provides the other half of the comparison.

understand. but I have another problem, -->focus on meaning CE ,
like "almost instantly a diesel locomotive could summon nearly full power from a cold engine" is different from the "the diesel locomotive could summon nearly full power from a cold engine almost instantly"
does some differences exists in meaning about C and E here?

Bad post again!!
Would like you to underline the part of the question under study and reveal the OA only with a spoiler!