Which of these is a unit rate?​

Acircle has a radius of 5/6 units and is centered at (3.6, 7.8) write the equation of this circle

Ineed to know the answer to this algebra question.

Determine the common ratio and find the next three terms of the geometric sequence. 10, 2, 0.4, a. 0.2; -0.4, -2, -10 c. 0.02; 0.08, 0.016, 0.0032 b. 0.02; -0.4, -2, -10 d. 0.2; 0.08, 0.016, 0.0032 select the best answer from the choices provided a b c d