Which of the following questions could best be answered by the work of christian doppler? a. how are mirrors used inside a camera? b. how quickly are stars in the milky way moving away from earth? c. what is the best way to deliver broadband internet service to rural areas? d. what is the maximum mass of a stable white dwarf star?

Option B

Explanation:

Given are four options and we must select one out of four which could be best answered by the work of Christian Doppler

Mirrors used inside a camera work on the point that light reflects from a mirror depending on the surface of the mirror and hence images formed

Broadband internet service to rural areas is the speed and reliability of the cables connecting internet to rural.

Maximum mass of a stable white dwarf star depends on the material used for making the car.  These three do not depend on doppler effect

But how quickly are stars in the Milky Way moving away from Earth depend on the relative speed of the source and the observer.  Hence in this Doppler effect is applied.