A medical research team tests for tumor reduction in a sample of patients using three different dosages of an experimental cancer drug. Which of the following is true?
(A)There are three explanatory variables and one response variable. (B)There is one explanatory variable with three levels of response. (C)Tumor reduction is the only explanatory variable, but there are three response variables corresponding to the different dosages. (D)There are three levels of a single explanatory variable.
D