What is the question stem askin for?
It is askinig us to find what is Qs answer possibly trying to oppose
This is a "inference" question which means we might have to make subtle inferences not
directly stated in the text.Lets look at the choices:
Paraphrasing: Q thinks that 85/90 year olds all using right hand probably menas nothng
more than a particular social norm followed during the childhood years of this age group.
and M has gone a little too far in attributing this pattern to perhaps a UNIVERSAL RULE
concerning human evolution and survival.
Lets see what the ansswer choice states:

A) Being born right-handed confers a survival advantage.
There is a slight hint that M might try to relate a persons age(and hence his
disposition of survival for such a long time) to his left handedness..keep it

(B) Societal attitudes toward handedness differ at different times.
nowhere has M mentioned about changing times,he is clearly talking about a specific
age group..OUT

(C) Forcing a person to switch from a preferred hand is harmless.
M is noway referring to a force or a switch or a harm.OUT

(D) Handedness is a product of both genetic predisposition and social pressures.
M just tries to link age to a habit and most probably
inferring a relationship between longevity and right hand usage.He is not trying to
venture into the reasons OUT

(E) Physical habits learned in school often persist in old age.

M: It is almost impossible to find a person between the ages of 85 an 90 who primarily uses the left hand.
Q: Seventy to ninety years ago, however, children were punished for using their left hands to eat or to write and were forced to use their right hands.

Q's response serves to counter any use by M of the evidence about 85 to 90 year olds in supports of which one of the following hypotheses?
(A) Being born right-handed confers a survival advantage.
Correct : It is asking for what is Q trying to argue against with his/her response or also means what could M be trying to prove with the evidence that you can't find anyone 85/90 years old using left hands....so the logical answer would be that he might be trying to prove that right handed people live longer...therefore survival advantage..

(B) Societal attitudes toward handedness differ at different times.
Incorrect : Does not mention how the attitudes differ

(C) Forcing a person to switch from a preferred hand is harmless.
Incorrect : The stimulus does not mention whether changing to left handed is harmless

(D) Handedness is a product of both genetic predisposition and social pressures.
Incorrect : Irrelevant here

(E) Physical habits learned in school often persist in old age.
Incorrect : We are not sure whether these habits were learned in school