Which of the Following Statements Is True? A $\mathrm{SS}($

Which of the following statements is true? A. The sum of squares for treatments (SST) explains some of the variation.
B. The sum of squares for error (SSE) measures the amount of variation that is unexplained.
C. $\mathrm{SS}($ Total $)=\mathrm{SST}+\mathrm{SSE}$
D. All of these choices are correct.