A Disadvantage of the Quasi-Experimental Design Is That

A disadvantage of the quasi-experimental design is that

A) Researchers are unable to demonstrate a direct cause-and-effect relationship between the independent variable and the dependent variable.
B) The study has strict controls for variables such as age and ethnicity.
C) It contains 2 control groups rather than 1.
D) All of the above are disadvantages of the quasi-experimental design.