An investigation was carried out to measure the concentration of four substances (WWW, XXX, YYY, and ZZZ) in the tubular fluid of a healthy human nephron relative to their concentration in blood plasma. The graph below shows the results.

Which of the following correctly identifies substances WWW, XXX, YYY, and ZZZ?
WWW: Large proteins; XXX: Glucose; YYY: Urea; ZZZ: Sodium ions
WWW: Glucose; XXX: Large proteins; YYY: Sodium ions; ZZZ: Urea
WWW: Glucose; XXX: Large proteins; YYY: Urea; ZZZ: Sodium ions
WWW: Urea; XXX: Large proteins; YYY: Glucose; ZZZ: Sodium ions