How to roll of dc gain to unity via an opamp ac amplifier..?
Here is the gain formula (ideal opamp assumed):

G=1+R2/(R1+1/jwC)

As you can see, for w=0 the denominator approaches infinity and the second part of the sum disappears. Hence G=1. Note that the value of R2 plays no role since we assume (for an ideal opamP) that there is no current into the inv. input terminal (no voltage drop across R2).