Answer:
Independent Variable: different types of cancer drugs
Dependent Variable: tumor size
Constants: gender of patient, (type of cancer/tumor perhaps)
Step-by-step explanation:
The independent variable will always be what modifies the dependent variable to change. In this case, it is the different types of cancer drugs modifying the size of the tumor in the patients. Dependent variables are what get changed based off of what it is being modified by. The constants should be what stays the same throughout the experiment, or else it won't be a consistent one.