If the economy is at point c, what is the (oppurtunity) cost of 2 more automobiles?

Which statement about spreading knowledge of diseases and health around the world is correct?

According to the law of supply,suppliers want to sell their product at prices

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?