Which describes the relationship between human beings and the Earth system? A. Human actions affect the Earth system only minimally and temporarily.
B. Human actions are influenced by the Earth system but do not affect it.
C. Humans are a part of the Earth system, and their actions affect its parts.
D. Humans are independent of the Earth system.

1. beginning with all chambers of the heart in the "relaxed" phase, describe the cardiac cycle in mammals, with systole and diastole of the atria and ventricles. for each time point in the cycle you select, state the following: • whether the atria and ventricles are contracting or relaxing • whether the av valves and semilunar valves are closed or open • whether the pressure in the atria and ventricles is high or low