Final answer:
Diffusion involves the spread of molecules from a high concentration area to a low concentration area until a uniform concentration is reached, without using energy. Option 1.
Step-by-step explanation:
Diffusion is best described as the act of spreading something from one place to another. This is a passive process in which a substance, generally molecules, moves from an area of high concentration to an area of lower concentration, without the expenditure of energy. A common example of diffusion in biology is when molecules move within a cell's cytosol or when substances cross the plasma membrane. Over time, this process results in an even distribution of the substance throughout the space, creating a uniform concentration.