Studies Using Difference Scores Tend to Have Larger Effect Sizes

Studies using difference scores tend to have larger effect sizes than studies using other research designs because

A) of the long-standing procedural bias in psychology to set up studies involving dependent means in such a way as to artificially favor large effect sizes.
B) the standard deviation of difference scores is usually low.
C) participants provide their own baseline,which increases the variance.
D) studies with dependent means usually use a larger number of participants,so larger effect sizes are easily detected.