This bar graph would be MOST useful in a report about A) how political parties change over time.
B) why people change their party affiliation.
C) how the South consistently votes Democratic.
D) why conservative legislation fails in the Northeast.

Martha participates in a research study in order to receive extra credit for her psychology class. when she arrives in the research office she is given a can of what looks and tastes like beer, but which actually contains no alcohol. in the adjoining room martha's classmate karen is also participating in the study. karen receives a can of alcoholic beer. if the experiment was designed to test the effects of alcohol on concentration, then who is exposed to the independent variable?