Which of the following is true of factorial designs?

A) It eliminates the possibility of confounding variables.
B) All levels of each independent variable are combined with all levels of the other independent variable.
C) A control group is unnecessary.
D) The simplest factorial design has three independent variables, each having three levels.

Factorial designs involve manipulating two or more independent variables simultaneously, with all levels of each independent variable combined with all levels of the other independent variable(s). This allows for the examination of main effects of individual independent variables as well as their interaction effects. While factorial designs help minimize confounding variables, it does not completely eliminate the possibility of them. A control group may or may not be necessary depending on the specific research question or design, and there is no set number of independent variables or levels required for a factorial design.