Given This Hypothesis Answer the Following Two Questions

Multiple Choice

Given this hypothesis answer the following two questions. Ninth grade students enrolled in large classes who are taught algebra through the use of interleaved worked examples for each lesson perform better on an end of course test than are those taught with a single modeled example for each lesson.
-The independent variable in the above stated hypothesis is:

A) Type of instruction.
B) Ninth grade students.
C) Algebra.
D) End of course test.