A unit rate is a ratio that compares a quantity to 1. It is expressed as a fraction where the denominator is 1.
From the options given:
A. 7/5 - not a unit rate B. 3/4 - not a unit rate C. 1/27 - not a unit rate D. 27/1 - this is a unit rate because it can be interpreted as 27 of something per 1 of something.
Therefore, the correct answer is D. 27/1.