Mrs. S. is a 69-year-old critically ill woman who experienced a major hypotensive episode, secondary to gastrointestinal hemorrhage and hypovolemic shock. Mrs. S. had a massive gastrointestinal bleed last night. The bleeding has stopped, and she is now hemodynamically stable. However, her MAP (Mean Arterial Pressure) fell to less than 50 mmHg for more than 40 minutes. Mrs. S. has no unexpected complaints. She is very relieved that her stomach ulcer has stopped bleeding. Otherwise, she has only minor discomforts associated with treatment. Mrs. S.’s lying heart rate is 95 and blood pressure 138/84; standing heart rate is 100 and blood pressure 134/78. She is without jugular venous distension and experiences only fleeting vertigo when sitting. Mrs. S. has no dependent edema, her respiratory rate is 20 and unlabored, and her lungs have transitory rales that clear with coughing. Unfortunately, her urine output has been sluggish (15-20 ml/hr) overnight and has fallen to 10 ml/hr for the last 4 hours. The urine is a clear yellow. Urine specific gravity is 1.010, sodium 50 mEq/L, serum blood urea nitrogen 43 mg/dl, creatinine 1.3 mg/dl.

The probable reason for a drop in GFR and subsequent oliguria while Mrs. S. was bleeding was:
A. Rapid transfusions
B. Systemic acidosis
C. Systemic hypoxia
D. Lack of renal perfusion