Actually both a) and b) are correct.
About A): the two groups should be identical (but not the same, i.e. have the same attributes), only the treatment of them - the independent variable should be different.
But the one option to choose is b: The control group is identical to each test group except for one variable. This is the independent variable.
?? Why you want me to dooOOoOoOoOoo
Answer:
Class room environment ( i.e the type of wall)
Explanation:
Here, it is given that the two identical courses are being taught to the students that means the course is not varying.
Also, the same researchers are teaching the students that means the researchers are also not variables.
Therefore, the only thing that is varying in the whole research is the class room environment i.e the the walls of the classrooms.
In the glass walls there will be more distractions while in the opaque walls it will not be much.
Therefore, the classroom environment is the independent variable in the research.
