in a research study aimed to measure the most effective way to study, students are given a test on the material they reviewed. A group of ne15 was asked to take an exam after they read lecture summaries and after they watched and listened to lecture summaries. The researcher noticed that once a student took the test the first time, they were able to get through the exam faster the second time. What should the researcher have done to avoid this problem? a. Give the test at different hours of the day b. Create different test for the students c. Give the test in different languages d. Switch the order of study methods for the participants before the test