When the material that exits is lesser in amount than that of the entering material in a black box experiment, the parts of the system need to be changed.
In a black box experiment, the experimenters need to make assumptions regarding the drawing of conclusions. One such conclusion is the amount of material that exits.
If such amount is lesser than the one that enters the system, such experiment concludes that it is the time to change the parts of the system.
Hence, option D holds true regarding the black box experiment.
Learn more about black box experiment here:
https://brainly.com/question/13403296
#SPJ1