Go B go
The correct form would be "interest rates are tied to the prime not only on .. but also on ..."
A - incorrect because the sentence seems convey the wrong meaning (... not only are interest rates tied to the prime but they are also ...)
C - again "tied to the prime" is incorrectly positioned in the sentence.
D - incorrect because the sentence seems to convey the wrong meaning (... not only interest rates on loans to ... are tied to the prime but also something else on the loans is tied to the prime ..)
E - is missing the "on" after the "but also"
Try and try until you succeed! There is just no giving up!