An Experimental Group Listened to 10 Minutes of a Mozart

Multiple Choice

An experimental group listened to 10 minutes of a Mozart sonata, a control group listened to 10 minutes of relaxation to instructions, while the other control group listened to silence. The Mozart group performed much better on a subsequent test of spatial abilities than the two control groups. The results of this experiment are not valid because

A) 10 minutes is an inadequate amount of time.
B) There could be confounding variables.
C) The amount of time is not indicated for the group who listened to silence.
D) There are two control groups.