In What Way Does High Within-Groups Variance Obscure Between-Groups Variance

Multiple Choice

In what way does high within-groups variance obscure between-groups variance?

A) It leads to smaller effect sizes.
B) It limits the type of statistical analyses that can be conducted.
C) It causes more overlap between experimental/comparison groups.
D) Both a and c obscure between-group variance.
E) Both b and c obscure between-group variance.