Federally imposed restrictions on how much they pay small savers has created difficulties for savings banks as they are competing with such unregulated investment vehicles as money market certificates.

a. same as above.
b. has made it difficult for savings banks competing with such
c. have created difficulties for savings banks as they are competing with
d. have made it difficult for savings banks to compete with such
e. have made it difficult for savings banks as they are competing with such.

I think it's (c). However, I could not be 100 percent sure. d and e sound fine too but the problem I thought is "It" in the both answer choices. Can someone explain how to handle this?