What extent does a good imitation should be to ? Briefly,what he said is to be like , if we can achieve "yes " is much better, but it's not necessarily to achieve, "Yes. " "Like"refers to the mimic's voice,tone and so on. are very close to the imitation of the language, "Yes"is the voice,tone. and so on.are not only very close ,,but also very realistic to the imitation of the sound. Basically the voice is ,alike,just can be taken as real ones. We do not require and can not achieve this level.(Only reference,Hope help you)
To what extent imitation isn't imitate ok? Simple he said is to "like", if can achieve "is" is better, but not to want to achieve "is". "Like" refers to the pronunciation, intonation imitator, etc. Are all very close to the language, "imitated by not only in speech is" is. Intonation, etc are close to the imitated by voice, and very realistic. Even the voice also are basic and same, it can be genuine. We do not require also impossible to achieve this level.