A 53-Year-Old Woman Is Found, by Arteriography, to Have $50 \%$

A 53-year-old woman is found, by arteriography, to have $50 \%$ narrowing of her left renal artery. What is the expected change in blood flow through the stenotic artery?

A) Decrease to $1 / 2$
B) Decrease to $1 / 4$
C) Decrease to $1 / 8$
D) Decrease to $1 / 16$
E) No change