a student passes through a door two students pass by each other two students bump into each other students pass from a crowded room into a hall
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Which of these would be a model of diffusion?
Possibilities:
- a student passes through a door
- two students pass by each other
- two students bump into each other
- students pass from a crowded room into a hall

students pass from a crowded room into a hall