To Study the Effects of a New Mathematics Textbook, 30

To study the effects of a new mathematics textbook, 30 students are randomly selected. Based on the scores of their achievement test, students are grouped into three groups (limited: 0-15, proficient: 16-30, advanced: 31-45) . Half of the students in each group are then randomly assigned to use the new textbook, while the rest of the students continue to use the old textbook. 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