Question 1086840
a.  Increases the numerator, which increases the t statistic making it more likely to be significant.  That makes sense, since the further apart are the means, the more likely significance will be reached.
b.Size of the samples increases the denominator in the denominator (where the SE is). That is the same as increasing the numerator.  All other things being the same, increasing the sample size increases the numerator and the likelihood of significance.
c. Increasing the sample variances increases the denominator and makes the t statistic smaller.   That makes sense, since the more variability, the less likely a difference in means will be as significant.