Hakeem is testing the effects of sunlight on samples of soil. which of these actions would introduce confounding variables into hakeem’s experiment? (this is multible choice question) a. he tests a theory that’s already been established. b. he tests multiple hypotheses at a time. c. he uses identical specimens when completing multiple trials. d. he adjusts the independent variable and records the effects. e. he uses different types of soil in each of his samples.