YouTube Would Like to Test the Hypothesis That the Average $$t \bar { x }$$

YouTube would like to test the hypothesis that the average length of an online video watched by a user is more than 8 minutes. A random sample of 37 people watched online videos that averaged 8.7 minutes in length. It is believed that the population standard deviation for the length of online videos is 2.5 minutes. YouTube would like to set ? = 0.02. The test statistic for this hypothesis test would be --------- .

A) $$t \bar { x }$$ = 1.89
B) $$z \bar { x }$$ = 2.23
C) $$z \bar { x }$$ = 1.70
D) $$t \bar { x }$$ = 2.06