The answer is external stimulus
<span>Some of the things that would make the experiment invalid would be, if there was a variation in the behavior of the class with respect to food - for example, if some people ate their breakfast earlier than the others. This then would mean that some students would have already digested their breakfast during the morning classes and the others would still be digesting. </span>
Answer:
Tartar.
Explanation:
Dental plaque may be defined as the development of mass or biofilm of bacteria that grows on teeth surface. This plaque may present on teeth, between the teeth and on teeth front.
The plaque is first colorless but when it changes to dental calculus or tartar, the color of plaque becomes yellow or pale brown. This causes dental problem and different dental disease.
Thus, the answer is plaque.
