True // False: comparing means. Determine if the following statements are true or false, and explain your reasoning for statements you identify as fal

True // False: comparing means. Determine if the following statements are true or false, and explain your reasoning for statements you identify as false.
(a) When comparing means of two samples where $n_1=20$
and $n_2=40$,
we can use the normal model for the difference in means since $n_2\ge 30.$
(b) As the degrees of freedom increases, the t-distribution approaches normality.
(c) We use a pooled standard error for calculating the standard error of the difference between means when sample sizes of groups are equal to each other.