It is difficult to distinguish between colors at night because

Ais a group of people living and working under a set of rules and traditions.

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?

Pedestrians,cyclists,skateboarders,and highway construction workers are know as?