Which of the Following Statements Best Explains the Observation That

Multiple Choice

Which of the following statements best explains the observation that proton pumps are used by organisms in every domain of life?

A) Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life.
B) The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism.
C) Cells of each domain evolved proton pumps independently when oceans became more acidic.
D) Proton pumps are necessary to all cell membranes.