I think it's d. THEN AGAIN i am not completely sure
Answer:
I think its B they both got each other's ideas and goods
In assessing the internal validity of an intervention, we try to determine if certain changes cause certain outcomes. It is relevant in studies that try to establish casual relationship. While in observational or descriptive studies, it is not that relevant. It is also possible to have internal validity in a study and not have construct validity. Example, imagine a study where you are looking at the effects of a new computerized tutoring program on math performance in first grade students.
