The Advantage of Squaring the Deviation of Each Score from the Mean

The advantage of squaring the deviation of each score from the mean and then summing is that

A) it makes the sample variance an unbiased estimator of the population variance.
B) it makes the degrees of freedom for sample variance equal to n - 1.
C) it produces a minimal positive solution that is not zero, as long as all scores are not exactly the same value.
D) it makes the sample variance an unbiased estimator of the population variance and it produces a minimal positive solution that is not zero, so long as all scores are not exactly the same value.