You have been called to a local nursing home for a restless patient with a​ four-day history of diarrhea. The primary assessment reveals an open​ airway, rapid​ breathing, and a weak and rapid radial pulse. Vital signs are​ pulse, 124;​ respirations, 24​ breaths/min; blood​ pressure, 100/​ mmHg; and​ SpO2, 95%. The patient is confused with a history of​ Alzheimer's dementia. For this​ patient, it is most important to evaluate​ for:
A. Intestinal obstruction
B. Cause of confusion
C. Blood in the diarrhea
D. Dehydration