PJ Conducts an Experimental Study on the Effects of Soft

Multiple Choice

PJ conducts an experimental study on the effects of soft music during high stakes science testing. He randomly assigns students at the school. In one condition he does not provide music for testing while in the other group he does provide the music. He administers a pretest at the beginning of the year and a posttest at the end of the year. One concern in his study is that during the year the music teacher at the school he administered the study shared with students the physiological benefits of soft music.
-The introduction of the benefits of music during the duration of his study can be considered which of the following threats?

A) History
B) Maturation
C) Mortality
D) Testing