The diameter of the sun is about 1.4x10^6 km. The diameter of the planet Mercury is about 5000 km. What is the approximate ratio of the diameter of the sun to the diameter of mercury?
A. 2.8 x 10^2
B. 3.6 x 10^2
C. 2.8 x 10^3
D. 3.6 x 10^-3​