An Experiment Is Conducted to Assess the Effects of Two

An experiment is conducted to assess the effects of two types of reading improvement lessons: speed reading versus comprehension training. The subjects, high school seniors, are divided into two groups. Members of one group receive comprehension training from their high school English teacher, while at the same time the other group receives speed reading training from a local college instructor. What variables are confounded in this study?

A) speed reading and comprehension training
B) type of improvement lesson and the particular instructor
C) type of improvement lesson and year in school
D) year in school and the particular instructor