The North American Free Trade Agreement (NAFTA) is an agreement among the United States, Mexico, and Canada. The purpose of the agreement is to A.
simplify immigration laws among the three countries.
B.
make international travel easier among the three countries.
C.
call off most tariffs on trade among the three countries.
D.
combine the natural resources among the three countries.

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?