This diagram depicts a nephron. letter a is the beginning of the nephron, which is an enlarged sphere-shaped capsule that contains a mass of capillaries. a tube extends from the outer layer of the sphere, which travels in a convoluted way for a short distance. this tube then descends down and curves back along itself, forming a long loop. after finishing its ascent along the loop, the tube continues to travel in a convoluted way for a short distance until connecting to a darker-colored and wider tube that descends down and off of the page.

based on the cross sections above, which of the following correctly matches the structure with its function?

a—transports egg cells
b—transports sperm cells
c—transports sperm cells
d—transports egg cells