A scientist wants to know if the use of vitamin supplements reduces the recovery time from a certain surgery. They randomly select 50 patients who have had the surgery. They give 25 of the patients vitamin suppliments and 25 of the patients receive inactive treatment that resembles a vitamin supplement. The researcher studies the difference in recovery times between the two groups.

To analyze the results the researcher should use

A) one-sample z test

B) two-sample t test

C) one sample t test

D) the matched pairs t test