The answer is D. Environmental
C) Nothing in this world is limited. Especially your knowledge. You can teach an old dog knew tricks. Hope this helps
Cereal companies are blamed for putting too much sugar into their products, which causes obesity. This is bad for them, as it would stop people from bying their products. So they would have an interest in study showing that this is not the case: the study would be a self-interest study (the correct answer) and therefore not be reliable
