... intravenous injection to each member of a group of human subjects. The plasma drug concentrations were then determined at various time intervals. Two hours after drug administration, the mean plasma drug concentration of the subjects was 40 mg/L. Fourteen hours after drug administration, the mean plasma drug concentration was 5 mg/L.

Q1: What is the drug's elimination half-life?

A 1 hour
B 2 hours
C 3 hours
D 4 hours
E 6 hours