A Researcher Is Interested in Testing the Effectiveness of Using

Multiple Choice

A researcher is interested in testing the effectiveness of using "clickers" for question-and-answer sessions during lectures.He asks students in the morning section of his course to use clickers to respond to in-class questions.Students in the afternoon section write answers to questions in their notebook.He compares the students' average test performance for the two sections.The researcher will not be able to interpret the results because his study is flawed due to

A) his limited ability to generalize his results to other students and courses.
B) the confounding of class section (morning, afternoon) and response method (clicker, notebook) .
C) his failure to manipulate an independent variable.
D) the correlation between response method (clicker, notebook) and test performance.