Joel claims that “Bright White Toothpaste” removes tooth enamel stains better than all other brands. Which of the following should be documented as evidence to support his claim? 1. The amount of toothpaste used
2. The shade of teeth before and after brushing
3. The type of toothbrush used to brush teeth
4. The size of tooth

2. The shade of teeth before and after brushing

The independent variable in this instance is the bright white toothpaste, and if they’re claiming that it removes stains better than all, then that means that the dependent variable would be the shade of teeth!

The amount of toothpaste, the type of tooth brush, and the size of tooth are all variables of the experiment but will not determine if the claim is supported or not.

Hope this helps:)!