Given the following information about a hypothesis test of the difference between two means based on independent random samples from two normally distributed populations with unknown but equal variances, which one of the following is the correct rejection region at a significance level of .05?

A>B, X1= 12,X2= 9,s1s= 3,s2= 2,n1= 13,n2= 10

a.RejectH0if z > 1.96

b.RejectH0if z > 1.645

c.RejectH0if t > 2.08

d.RejectH0if t > 1.782

e.RejectH0if t > 1.721