[just_md]

or to simple - choice C, assuming no Phe deletion present in 508.
or more complicated - any of other choices, amino acids 433−586 in CFTR NBD-1

 

[just_md]

Wait a minute
Somebody please explain for me the whole issue.
I did not understand the question neither it's answer

CFTR - Cystic fibrosis transmembrane conductance regulator. Mutation in CFTR leads to cystic fibrosis. In stem no word about CF.
Now only pure logic - we know that deletion of Phe in 508 leads to CF. From present choices, only C has Phe inside. So, assuming that no mutation present in transmembrane segment, what else we have to do, --> Phe is present --> choice C. May be they are non-polar on second look, but pure logic more fast .
I don't know exact order in CFTR and don't want to know, because in this segment are amino acids from 433 to 586