Which of the Following Statements Are True of Tubular Secretion

Which of the following statements are true of tubular secretion (Select all that apply) ?

A) Hydrogen ions may be secreted in response to a decrease in the pH of the blood.
B) The metabolic products of medications may be secreted into the peritubular capillaries.
C) Creatinine is a nitrogenous waste product that may be actively secreted.
D) Tubular secretion takes place from the renal tubules to the peritubular capillaries.