The research method that identified the cause-effect relationship lies between the variables is known as the experimental method.
The following information regarding the experimental method is as follows:
- It includes the changes made in one variable in order to measure the cause made in the change in the other variable.
- It believes in the methods that are controlled, changes of the variables for testifying the hypothesis.
- Also, it identified the cause-effect relationships.
So, the other options are incorrect.
Therefore we can conclude that option a is correct.
Learn more about the variable here: brainly.com/question/19585043
