ANS:C - greater than the feedback resistance

It's for the purpose of averaging, if you would look at the formula Vo = (-Rf) ( (Sum of Vin) /Rin) for it to perform the averaging process, (Rf/Rin) should represent the number of inputs.

So for example you have 3 inputs, Rf/Rin should be equal to 1/3 so that Vo = (Sum of Inputs)/3, which is just the average of the inputs. If Rf becomes greater than Rin then it is now a Scaling Adder.