Which of the following events is not an example of diffusion?
a. while still some distance away, the smell of apples from a nearby fruit stall becomes very evident.
b. a person pouring water from a pitcher into a glass to get a drink
c. the exchange of oxygen and carbon dioxide in the lungs’ air sacs as a person respires.
d. a blue copper (ii) sulfate crystal dissolves slowly when placed in a beaker of water without stirring, giving a uniformly light blue solution.