The Phosphate Transport System in Bacteria Imports Phosphate into the Cell

The phosphate transport system in bacteria imports phosphate into the cell against the phosphate concentration gradient.The energy for phosphate import is provided by a pH gradient across the membrane (lower pH outside the cell than inside the cell) ,rather than by ATP hydrolysis.The bacterial phosphate transport system is an example of

A) passive diffusion.
B) facilitated diffusion.
C) active transport.
D) cotransport.
E) receptor-mediated endocytosis.