New assistant principals Bernice and Leah wanted to determine the effect of three experimental ELA curricula on improving learning outcomes for EL and ED students. Students in their high school were randomly assigned to one of the three new ELA curricula intended to improve content knowledge in ED and EL students. Pre-test and post-test measurements of the treatment (new ELA curriculum) outcomes, resulted in a score determined by the difference in the two scores. The data differences were gathered and entered into a spreadsheet in the form of an improvement score. Again, the improvement score was based on the pre- and post-treatment (curricular) assessments. Identify the independent variable(s) in their study: a. The new EL curricula focused on ELA b. The new ED curricula focused on ELA c. The new ELA curricula focused on ED and EL students d. The improvement scores