Ravi Was Studying the Effect of a New Medicine on Subjects

Ravi was studying the effect of a new medicine on subjects' blood pressure. He randomly sampled 60 laboratory rats and ranked them based on their current blood pressure. Those ranked from 1 to 3 (i.e., the three rats with the highest blood pressure) formed group 1, and those ranked from 4 to 6 formed group 2, etc. Ravi then randomly selects five groups (i.e., 15 rats) . Within each group, rats were randomly assigned to three groups: new medicine, old medicine, and no medicine. Which of the following methods of blocking is employed here?

A) Predefined value blocking
B) Predefined range blocking
C) Sampled value blocking
D) Sampled range blocking
E) Post hoc blocking method