【单选题】

The illuminationE， in foot candles，provided by a light source of intensity I，in candles，at a distanceD，in feet，iSgiven by

For an illumination of50 foot candles at a distance of 4 feet from a source，the intensity of the source must be
A、50 candles
B、200 candles
C、800 candles
D、1，600 candles
E、2，500 candies