In the induced-fit model of enzymes, a substrate associates itself with which part of an enzyme?
a) the denatured site .
b) the amino acid site .
c) the active site .

That would be the "active site".  There are three parts to the induced-fit model.  The substrate, the enzyme, and the active site.  The enzyme and the substrate form together like two puzzle pieces, and the active site is the space in between the two puzzle pieces.  It is still there when the enzyme and substrate have connected.  I hope I helped!  If I have wrong information, or you don't understand my analogy, please inform me so I can fix it.  :D  Thanks!

In the induced-fit model of enzymes, a substrate associates itself with the active site of the enzyme. So, the right answer will be the C.

That would be a working theory.