A unit rate is a ratio that compares a quantity to one unit of another quantity. For example, if you want to express miles per hour or price per item, the unit rate would be in the form of "x/1" or similar.
Among the options provided, the fraction that represents a unit rate is:
27/1 (Start Fraction 27 over 1 End Fraction)
This fraction implies that there are 27 of something for every 1 of another quantity, which fits the definition of a unit rate.