In the Context of ANOVA, an Eta-Squared Is Used to Portray

In the context of ANOVA, an eta-squared is used to portray which of the following?

A) The degree of statistical significance of mean differences
B) The necessary sample size to obtain a statistically significant result
C) The proportion of error variability in the population the study failed to account for.
D) The proportion of variability explained by one variable on another variable.