In addition to equal variances, what other assumption is necessary in (a)? A. In addition to equal variances, it must be assumed that the population sizes are equal. B. In addition to equal variances, it must be assumed that the samples are specifically chosen and not independently sampled. C. In addition to equal variances, it must be assumed that the sample means are equal. D. In addition to equal variances, no other assumptions must be made because the sample sizes are large enough (greater than or equals30 for each sample)