The formal method of study that the student describes is using the scientific method. The correct option is c.
What is a scientific method?
A scientific method is a method that uses calculations, interpretations, and logic to come to a conclusion. Scientific methods are used to calculate the actual results of scientific studies. The result is calculated by using scientific tools.
Here the use of grocery bags impacting the environment is the main viewpoint. The grocery bag that is made up of cloth will less impact the environment than those which are made up of plastic or paper. This can be measured by the scientific data and results.
Thus, the correct option is c. using the scientific method.
To learn more about the scientific method, refer to the link:
https://brainly.com/question/7508826
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