Scientists are testing a new drug, which they think might allow people to memorize large amounts of information. Group A is taking a sugar pill. Group B is taking the new drug. Both groups are 25–35 years old and are not taking any other medicine. After a month, both groups will be given a memorization test, and scientists will compare each group’s ability to memorize new information. Which choice is the controlled variable (constant) in the experiment? A. the sugar pill B. the new drug C. the ability to memorize D. the age of the test subjects
