Fact 1 :- The hynotised subjects are told that they are deaf . Right ? Yes
Fact 2 :- When asked whether they can hear hynotist , they replied "No" . Right ? Yes

But point to wonder is that if they are deaf , how can they hear the question asked ???

Hope that helps.

I am not reading the answer choices yet. Trying to analyze the argument and offer the challenges for picking up.

Conclusion:
Some theorists try to explain this result by arguing that the selves of hypnotized subjects are dissociated into separate parts, and that the part that is deaf is dissociated from the part that replies.

Premise:
When hypnotized subjects are told that they are deaf and are then asked whether they can hear the hypnotist, they reply, "no."

There is a gap between premises and conclusion - new information has been introduced in the conclusion (read below about the gaps)

gap No 1
... the selves of hypnotized subjects are dissociated into separate parts

gap No 2
... and that the part that is deaf is dissociated from the part that replies

We are put to believe that the conclusion made about the hypnotized subjects is true based on some theorists' arguments (hypotheses). Further, we are put to believe in argued relationship of two dissociated parts which reply independently - one says "Deaf" and the other acts as not "Deaf" by speaking out the words.

Challenge No 1
When the hypnotist tells the subject about the latter being "Deaf" and the subject replies "No" does that really mean that the subject acts as Deaf? It could be as well that the subject replies "No" being under some influence which is unrelated to the dissociated parts at all.

Next, challenge is related to the premise which contains condition: "When hypnotized subjects are told that they are deaf and are then asked ..." Does the conclusion really take into account whether the subjects act as "Deaf" when they are told that they are "Deaf"?

Challenge No 2
The conclusion only says that the subject under hypnosis is dissociated into separate parts. BUT the conclusion does not say that subject's dissociated part acts as "Deaf" when the subject is told that the one is "Deaf". Therefore, we may imply that one of the dissociated subjects as stated in the conclusion acts as "Deaf" without being told anything.

So the question may arise that the answer "No" which is contained in premise and not listed in the conclusion could be changed to the answer "Yes"? if we manage to do so and ask ourselves can the subject answer "Yes" for sure we will put the threat onto the conclusion itself with all the challenges stated above. A reply of the subject may not be related to the condition when the subject is "Deaf", because one may well answer "Yes" ...