A 45-year-old male presents with oliguria. He is diagnosed with chronic glomerulonephritis. Oliguria is related to:
A. thickening of the glomerular membrane and decreased renal blood flow.
B. increased glomerular capillary oncotic pressure and tubular obstruction.
C. activation of renin-angiotensin from decreased blood volume.
D. vasoconstriction of the efferent arterioles.
Answer: A