The diagram shows a firefighter operating a hose. The arrows show the forces acting on the hose. Which statement describes the situation in the diagram?
A. Since the firefighter is at rest, he does not move as he operates the hose.
B. The hose has very little friction, making it slide toward the firefighter.
C. The firefighter's mass decreases the forc
the water escaping from the hose.
D. The water escaping from the hose exerts an equal and opposite force on the hose.

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?