The diagram shows a simplified section through a renal corpuscle in a mammalian kidney.

Which part, A\text{A}A, B\text{B}B, C\text{C}C, or D\text{D}D, represents the efferent arteriole, which carries blood away from the glomerulus and has a narrower lumen to maintain the high hydrostatic pressure required for ultrafiltration?
A\text{A}A
B\text{B}B
C\text{C}C
D\text{D}D