Which Statement Is NOT Characteristic of an Active Transport System

Which statement is NOT characteristic of an active transport system for L-alanine in animal cells?

A) L-alanine is transported against a concentration gradient.
B) A carrier protein is required to recognize and bind L-alanine.
C) It is blocked by inhibitors of oxidative phosphorylation.
D) It transports D- and L-alanine with equal facility.
E) It is functional in renal tubular cells.