In 1990, the average duration of long-distance telephone calls originating in one town was 9.3 minutes. A long-distance telephone company wants to perform a hypothesis test to determine whether the average duration of long-distance phone calls has changed from the 1990 mean of 9.3 minutes. Formulate the null and alternative hypotheses for the study described.

A.

H_o: = 9.3 minutesH _a : < 9.3 minutes

B.

H_o: = 9.3 minutesH _a : > 9.3 minutes

C.

H_o: = 9.3 minutes H _a : 9.3 minutes

D.

H_o: 9.3 minutesH _a : = 9.3 minutes