At 4 AM, the hemodynamic monitor for a critically ill client in the intensive care unit indicates that the client's mean arterial pressure is at the low end of the normal range; at 6 AM, the client's MAP has fallen definitively below normal. The client is at risk for

A. left ventricular hypertrophy.
B. pulmonary hypertension.
C. organ damage and hypovolemic shock.
D. orthostatic hypotension.