SC.. Question about the Original Sentence

[Abdulla]

Could we assume that the original sentence is always contains the correct meaning ?

[JonathanSchneider]

Not exactly. You can assume that the intended meaning of A is always the meaning we want. However, oftentimes there is a clarity issue in A that requires us to fix it by picking some other choice. Most of the time this is a simple choice: we choose some other option that makes the intended meaning more clear. Very occasionally you may find that you must pick a choice that slightly changes the meaning in order to preserve grammatical correctness; these cases are rare, though, and the meaning change is usually very slight.