Selecting and Recruiting Subjects When There Is a Statistically Significant

Selecting and Recruiting Subjects When there is a statistically significant difference between two treatment groups, we know that

A) extraneous variables did not confound the study.
B) random assignment created groups that were identical on the dependent variable before the researcher manipulated the independent variable.
C) the effect size of the independent variable is very large.
D) the independent variable produced group differences on the dependent variable that are larger than we would expect due to chance.