Answer: The independent variable is the dose of the medication administered to the patients.
Explanation: The independent variable is the factor that is deliberately changed or manipulated by the researcher to observe its effects on the dependent variable. In this case, Dr. DeJesus is varying the doses of the medication given to the patients to see how it affects the number of malignant tumors. The number of malignant tumors would be the dependent variable because it is what is being measured or observed as a response to the different doses.