The major protein component of human hair is α-keratin.

Hair ‘straighteners’ are commonly used tools which use heat
to iron hair into temporarily lying flat and straight. What is
the best biological explanation for this phenomenon?
a. Hair straitner denatures protein by disrupting the PH
b. Hair straitner disrupt hydrogen bonds in α-keratin
c. Hair stratner disrupt ionic bonds between α-keratin
molecules
d. Hair straitner disrupt disulphide bridges in α-keratin

d. Hair straitner disrupt disulphide bridges in α-keratin.

The best biological explanation for the phenomenon of hair straighteners temporarily straightening hair is that they disrupt the hydrogen bonds in α-keratin. The correct option would be b.