2 5 i - 9 4 9 1 12 1 15 Question 7 (1 point) Saved Which of the following statements about buffer solutions is true? They maintain a constant pH when acids are added to them but not when bases are added to them. They are found only in living systems and biological fluids. They maintain a relatively constant pH when either acids or bases are added to them. They maintain a constant pH when bases are added to them but not when acids are added to them. They maintain a relatively constant pH of approximately 7 when either acids or bases are added to them