10. The PICO test used questions that students were unfamiliar with at the start of the study. For example, students saw test items like the one below: Number: Mittens Underline the amount of mittens these children need in total On the PICO post-test, students saw the same pre-test PICO questions, which were much easier to answer since the students had seen the items before. The researchers found that students in the math-based reading program and the control reading programs performed similarly on the PICO post-test at the end of the study. Which internal validity threat is most likely occurring in this scenario? a. Maturation b. Regression to the mean c. Selection d. Mortality e. Instrumentation f. Testing g. History h. Interactions i. Diffusion j. No Threat