What is the relationship between the apparent brightness of any light source and the distance from the light source to the observer?
选项：

A:The apparent brightness is proportional to the distance from the light source to the observer.;
B:The apparent brightness is proportional to the square of the distance from the light source to the observer.;
C:The apparent brightness is inversely proportional to the distance from the light source to the observer.;
D:The apparent brightness is inversely proportional to the square of the distance from the light source to the observer.