Answer: Fats
Explanation:
I learned this in 5th grade, you can also Google it if you don't believe me.
In a study, the independent variable is the thing that you change to see how the change produces different results. In this study, the independent variable would be the use of nicotine.
The tooth's outer layer consists of the Enamel, Dentin and the Pulp.
<h3>What is a tooth?</h3>
A tooth is a hard resistant structure that is located in the mouth for crushing down before swallowing and digestion.
The tooth's outer layer consists of the Enamel, Dentin and the Pulp. The Enamel is the toughest of them all and located at the top layer of the teeth while the dentin is beneath the enamel layer of the teeth with the pulp in the middle.
Learn more on tooth layer here: brainly.com/question/10929330
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