Doesn't need an input of energy of the cell. (fill in the blank)

Passive transport

Explanation:

There are two ways molecules can get in and out of the cell. These processes are called Passive and Active transport.

Passive transport is the movement of molecules and materials from high to low concentration. No energy is needed for this process because it happens naturally.

This is in contrast to what Active transport is, where energy is needed because it moves the molecules or materials against the concentration gradient where they move from lower to higher concentration.