To Measure the Effects of Task Complexity on an Individual's

Multiple Choice

To measure the effects of task complexity on an individual's perception of time,a researcher has one group of participants do simple addition problems and another group solve complex mathematical formulas.Both groups are then asked to estimate the time elapsed since they began the task.Later,the researcher finds out that the participants given the complex task were in a room with higher noise levels than the other group.In this study,which term best describes the noise level?

A) the placebo effect.
B) a dependent variable.
C) a confounding variable.
D) an independent variable.