All of the following processes require the cell to use atp energy, except

a) endocytosis.
b) active transport.
c) passive transport.
d) the sodium-potassium pump.

Ans. (C). passive transport.

ATP or adenosine triphosphate can be described as the principle molecule that provides energy for nearly all cellular activities that require energy. The endocytosis, active transport and sodium-potassium pump are energy-dependent processes that require breakdown of ATP molecules to release energy.

The passive transport is an energy-independent process, which does not use ATP energy. It involves transport of non-polar, uncharged molecules and some small polar molecules through lipid bilayer.

Thus, the correct answer is option (C).